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Old 14 Jul 2017, 09:02 AM   #1
camner
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Join Date: Jul 2002
Location: Tacoma, WA
Posts: 545
spam getting through custom sieve rules

I have custom sieve rules set up to discard mail sent to certain addresses. When I test the script by sending myself an email to one particular address on the "discard" list, the email correctly gets discarded. But certain emails from outside spammers to that same email address get through, and I don't understand why. I have run my Sieve code on this particular email through Sieve Tester, and sure enough, it gets through.

The only reference to a "To" address I could find is highlighted in red in the message below, which is the email address that is in my Sieve script to be discarded, and as I indicated, sending myself an email to that address does result in the email being discarded.

Am I misreading the headers and is the email actually being sent to a different address?

Thanks for any help you can be.

Here's the raw headers:
Code:
Return-Path: <mlopez@oben.com.co>
Received: from compute5.internal (compute5.nyi.internal [10.202.2.45])
	 by sloti38d1t06 (Cyrus fastmail-fmjessie44472-15312-git-fastmail-15312) with LMTPA;
	 Thu, 13 Jul 2017 15:41:18 -0400
X-Cyrus-Session-Id: sloti38d1t06-281765-1499974878-2-2414931264603118082
X-Sieve: CMU Sieve 3.0
X-Spam-known-sender: no
X-Spam-score: 6.2
X-Spam-hits: BAYES_40 -0.001, DIET_1 0.001, MISSING_SUBJECT 1.799,
  RCVD_IN_BL_SPAMCOP_NET 2, RCVD_IN_INVALUEMENT 2, SPF_HELO_PASS -0.001,
  SPF_PASS -0.001, URI_NOVOWEL 0.5, LANGUAGES en, BAYES_USED user,
  SA_VERSION 3.4.0
X-Spam-source: IP='190.145.99.75', Host='mail.casaoben.com', Country='CO',
  FromHeader='co', MailFrom='co'
X-Spam-charsets: 
X-Resolved-to: myFMname@fastmail.com
X-Delivered-to: sp@myfmdomain.com
X-Mail-from: mlopez@oben.com.co
Received: from mx3 ([10.202.2.202])
  by compute5.internal (LMTPProxy); Thu, 13 Jul 2017 15:41:18 -0400
Received: from mx3.messagingengine.com (localhost [127.0.0.1])
	by mailmx.nyi.internal (Postfix) with ESMTP id 03D7446444
	for <sp@myfmdomain.com>; Thu, 13 Jul 2017 15:41:18 -0400 (EDT)
Received: from mx3.messagingengine.com (localhost [127.0.0.1])
    by mx3.messagingengine.com (Authentication Milter) with ESMTP
    id 01EBEB883D7;
    Thu, 13 Jul 2017 15:41:18 -0400
Authentication-Results: mx3.messagingengine.com;
    dkim=none (no signatures found);
    dmarc=none (p=none) header.from=oben.com.co;
    spf=pass smtp.mailfrom=mlopez@oben.com.co smtp.helo=mail.casaoben.com
Received-SPF: pass
    (oben.com.co: 190.145.99.75 is authorized to use 'mlopez@oben.com.co' in 'mfrom' identity (mechanism 'mx' matched))
    receiver=mx3.messagingengine.com;
    identity=mailfrom;
    envelope-from="mlopez@oben.com.co";
    helo=mail.casaoben.com;
    client-ip=190.145.99.75
Received: from mail.casaoben.com (mail.casaoben.com [190.145.99.75])
	(using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))
	(No client certificate requested)
	by mx3.messagingengine.com (Postfix) with ESMTPS
	for <sp@myfmdomain.com>; Thu, 13 Jul 2017 15:41:17 -0400 (EDT)
Received: from localhost (localhost [127.0.0.1])
	by mail.casaoben.com (Postfix) with ESMTP id D54FF196154B;
	Thu, 13 Jul 2017 09:28:35 -0500 (COT)
Received: from mail.casaoben.com ([127.0.0.1])
	by localhost (mail.casaoben.com [127.0.0.1]) (amavisd-new, port 10032)
	with ESMTP id V52moA6lzHma; Thu, 13 Jul 2017 09:28:35 -0500 (COT)
Received: from localhost (localhost [127.0.0.1])
	by mail.casaoben.com (Postfix) with ESMTP id 90EF91936437;
	Wed, 12 Jul 2017 18:21:00 -0500 (COT)
X-Virus-Scanned: amavisd-new at casaoben.com
Received: from mail.casaoben.com ([127.0.0.1])
	by localhost (mail.casaoben.com [127.0.0.1]) (amavisd-new, port 10026)
	with ESMTP id g-eHNeuIkBdp; Wed, 12 Jul 2017 18:21:00 -0500 (COT)
Received: from [127.0.0.1] (unknown [185.138.92.84])
	by mail.casaoben.com (Postfix) with ESMTPSA id E9BA018CDFE8;
	Wed, 12 Jul 2017 10:50:12 -0500 (COT)
Date: Wed, 12 Jul 2017 17:50:02 +0200
From: mlopez@oben.com.co
To: sp@aceplasticinc.com, sp@action-hi.co.uk, sp@aircomp.com, sp@asfc.ac.uk,
Message-Id: <20170712155012.E9BA018CDFE8@mail.casaoben.com>


: SMTPHEADER_REPLYTO#
MIME-Version: 1.0
Content-Type: multipart/alternative;
 boundary="--_com.android.email_56950588071180"
Message-ID: <eqt0ayh-b6i839-20@oben.com.co>

This is a multi-part message in MIME format

----_com.android.email_56950588071180
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

filterUsage=0 filterMask= negateFilter=0 plaintext=1 convertMsgBodyToImage=0 convertedMsgBody=%3Chtml%3E%3Cbody%3E%3Cimg+src%3D%22%23ATTACHIMG(1)%23%22%3E%3C%2Fbody%3E%3C%2Fhtml%3E delayedMessage=0 minutesToDelay=60 Both Short-Term And Long-Lasting Improvements: The Newest Diet Solution It’s never too late to start working on improving your body's natural weight loss system. Begin improving your health by learning more about our extraordinary diet product. All the powerful components are there to provide both momentary and lasting improvements, you will drop approximately 40 pounds or more, you will lose 4 inches or more off your waistline. The crucial part: you'll keep all of that off. You [wouldn’t|would not} believe the wonderful results that you can check on our official website. To learn all the information you need, click on this link http://www.google.com/url?q=http%3A%2F%2Feqhgr.goodlostfat2.top&sa=D&sntz=1&usg=AFQjCNGcaXtyk5hp8wTtnOEApw8mYE7_xQ

----_com.android.email_56950588071180
Content-Type: text/html; charset=UTF-8
Content-Transfer-Encoding: 8bit

filterUsage=0
filterMask=
negateFilter=0
plaintext=1
convertMsgBodyToImage=0
convertedMsgBody=%3Chtml%3E%3Cbody%3E%3Cimg+src%3D%22%23ATTACHIMG(1)%23%22%3E%3C%2Fbody%3E%3C%2Fhtml%3E
delayedMessage=0
minutesToDelay=60
Both Short-Term And Long-Lasting Improvements: The Newest Diet Solution
It’s never too late to start working on improving your body's natural weight loss system.
Begin improving your health by learning more about our extraordinary diet product.
All the powerful components are there to provide both momentary and lasting improvements, you will drop approximately 40 pounds or more, you will lose 4 inches or more off your waistline.
The crucial part: you'll keep all of that off.
You [wouldn’t|would not} believe the wonderful results that you can check on our official website.
To learn all the information you need, click on this link
http://www.google.com/url?q=http%3A%2F%2Feqhgr.goodlostfat2.top&sa=D&sntz=1&usg=AFQjCNGcaXtyk5hp8wTtnOEApw8mYE7_xQ

----_com.android.email_56950588071180--
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Old 14 Jul 2017, 03:06 PM   #2
Terry
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Posts: 2,487
Sorry I thought you were just testing your rules by sending yourself an email so what I said is pointless.

Last edited by Terry : 15 Jul 2017 at 11:13 AM.
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Old 14 Jul 2017, 03:14 PM   #3
n5bb
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Posts: 8,178
With regards to the To header, this depends on what you munged in the headers you posted. There are addresses in the To header, and I'm not sure if one is yours. There are usually three ways someone can send an email which is delivered to your account:
  • To header
  • Cc header
  • Bcc, which forces blind sending so does not place your address in the normal headers. If you receive a message, your email address will always be in the "envelope" To, which is just what the sending server tells the FastMail receiving server is the destination during the initial SMTP connection protocol. The envelope is normally hidden, but FastMail copies the envelope To into the X-Delivered-to normal header.
So you can see that custom sieve looking at the To header only discovers one out of the three delivery methods shown above. The normal rules are much easier to use, since the "Any recipient's email" condition catches all of the cases described above.

If you use a wildcard alias for your domain, a better way to block certain specific addresses is to make aliases for these addresses which are set to Reject all mail sent to this address. This causes that address to not exist at the SMTP receiving stage.

Bill
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Old 15 Jul 2017, 12:57 AM   #4
BritTim
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Location: mostly in Thailand
Posts: 2,467
It looks as Bill suggested that the message was delivered via bcc (the x-delivered-to header apparently is different from those in the To header). Maybe, you are missing a check of the x-delivered-to header in addition to To and Cc headers.

I also see that the message has a pretty big spam score of 6.2. I would look at the spam block in the sieve script to see what happens to messages with that spam score.
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Old 15 Jul 2017, 04:26 AM   #5
n5bb
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Posts: 8,178
I'm going to repeat two suggestions I made:
  • Use aliases set to reject delivery to block specific usernames at your own domain which spammers are using repeatedly. If they only do it a couple of times in a month it's probably not worth the trouble to block them.
  • Use the normal rules screen if at all possible (rather than custom sieve). The rules screen has many more features than in the past, and as I mentioned in my earlier post it's easy to use the "Any recipient's email" condition to catch a message no matter how it was sent (To/Cc/Bcc).
Also remember that the normal rules sieve processing order is as follows::
  1. Discard rules
  2. Spam filtering
  3. Forwarding rules
  4. Organize into folder rules
Bill
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Old 15 Jul 2017, 08:17 AM   #6
camner
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Location: Tacoma, WA
Posts: 545
Quote:
Originally Posted by n5bb View Post
With regards to the To header, this depends on what you munged in the headers you posted. There are addresses in the To header, and I'm not sure if one is yours. There are usually three ways someone can send an email which is delivered to your account:
  • To header
  • Cc header
  • Bcc, which forces blind sending so does not place your address in the normal headers. If you receive a message, your email address will always be in the "envelope" To, which is just what the sending server tells the FastMail receiving server is the destination during the initial SMTP connection protocol. The envelope is normally hidden, but FastMail copies the envelope To into the X-Delivered-to normal header.
So you can see that custom sieve looking at the To header only discovers one out of the three delivery methods shown above. The normal rules are much easier to use, since the "Any recipient's email" condition catches all of the cases described above.

If you use a wildcard alias for your domain, a better way to block certain specific addresses is to make aliases for these addresses which are set to Reject all mail sent to this address. This causes that address to not exist at the SMTP receiving stage.

Bill
Thanks for the reply.

I didn't munge any of the "To:" addresses because none of the ones listed are mine.

My Sieve code only looks at "From" and "To", so I think the next step will be to add "X-Delivered-to" to the list of headers to check. If I understand you correctly, if, for example, someone sends me an email with the email address <me@mydomain.com> in the BCC field, this email address won't show up in to "To" header but will be in the envelope header and will therefore be copied to the "X-Delivered-to" header. Do I understand this correctly?

If I understand this correctly, can I just use the "X-Delivered-to" header and skip the checking of the "To" header?
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Old 15 Jul 2017, 08:21 AM   #7
camner
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Quote:
Originally Posted by BritTim View Post
It looks as Bill suggested that the message was delivered via bcc (the x-delivered-to header apparently is different from those in the To header). Maybe, you are missing a check of the x-delivered-to header in addition to To and Cc headers.

I also see that the message has a pretty big spam score of 6.2. I would look at the spam block in the sieve script to see what happens to messages with that spam score.
Yes, I realized I'm missing a check of the x-delivered-to header.

The email ended up in my spam folder, which is good, but I'd rather simply delete email to certain addresses silently, because I have found that particularly with email addresses than once were legitimate (such as <dropbox@mydomain.com>, when these fall into the hands of spammers they are much more likely to end up in my inbox rather than in the spam folder (perhaps because FM remembers from a while back when the email was good?)
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Old 15 Jul 2017, 08:28 AM   #8
camner
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Posts: 545
Quote:
Originally Posted by n5bb View Post
I'm going to repeat two suggestions I made:
  • Use aliases set to reject delivery to block specific usernames at your own domain which spammers are using repeatedly. If they only do it a couple of times in a month it's probably not worth the trouble to block them.
  • Use the normal rules screen if at all possible (rather than custom sieve). The rules screen has many more features than in the past, and as I mentioned in my earlier post it's easy to use the "Any recipient's email" condition to catch a message no matter how it was sent (To/Cc/Bcc).
Also remember that the normal rules sieve processing order is as follows::
  1. Discard rules
  2. Spam filtering
  3. Forwarding rules
  4. Organize into folder rules
Bill
Thanks for these suggestions. I initially set up my custom Sieve rules before the Rules screen became so much sophisticated. Perhaps it is time for me to spend the time needed to move many of my custom rules to the "standard" Rules screen.

Can you explain a bit what you mean by ?Use aliases set to reject delivery to block specific usernames at your own domain"? Does this mean to set up an alias and just point it to "nobody"?
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Old 15 Jul 2017, 08:36 AM   #9
camner
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Posts: 545
A followup question related to writing Sieve rules. Currently my sieve rules for discarding mail to known "spammy" targets at my domain looks like this:

Code:
if anyof
      (
       # 1. 'matches' can contain wildcards, 'contains' cannot
         address :matches ["to","from"] 
         [
          "adobe@mydomain.com",
          "adobe1@mydomain.com",
          "adobe2@mydomain.com",
          "adbrs1@mydomain.com",
          and about 50 more!
        ],

       # 2. for partial match but cannot contain wildcards
         address :contains ["to"]
         [
          "info@mydo",
          "sales@mydo"
         ],

       # 3. by header
         #fastmail virus notifications
           header :is ["subject"] ["Infected file rejected"],
           header :contains ["subject"] ["fcyi.pk"],
           header :contains ["subject"] ["Undelivered Mail Returned"],
         #specific attachment
           header :is ["X-Attached"] ["email-info.zip"],
           header :is ["X-Attached"] ["email-text.zip"],
           header :is ["X-Attached"] ["email-doc.zip"],
           header :is ["X-Attached"] ["IMPORTANT.zip"],
           header :contains ["X-Spam-orig-subject"] ["ISO-2022-JP"]
      )
      {discard;stop;}
The #3 block was added a long time ago in response to suggestions on this forum for dealing with certain situations that were generating LOTS of spam in my inbox.

If I want to filter on the Envelope header or the X-delivered-to header, the only way I know to do that would be to add another block in the "anyof" series. But that would force me to repeat all of the nearly 50 email addresses I'm checking for in each block. Is there a fancier way of writing the Sieve code so I only have to list the email addresses once?
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Old 15 Jul 2017, 10:35 AM   #10
n5bb
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Posts: 8,178
Quote:
Originally Posted by camner View Post
...Can you explain a bit what you mean by ?Use aliases set to reject delivery to block specific usernames at your own domain"? Does this mean to set up an alias and just point it to "nobody"?
No, that's not what I meant.
  • Go to the Settings>Aliases screen.
  • Click New Alias at the top.
  • Enter a new email address at your domain, such as sp @ yourdomain
  • Removing the Deliver to address will not prevent messages sent to that alias from being delivered to your account.
  • But you can choose a Restrict senders policy of "Reject (bounce) all mail sent to this address (disable the alias)".
  • Click Save at the top to save and exit. Click Settings>Mail to go back to your message list.
If you have a wildcard delivery alias set up for your domain, the steps above will disable a single alias at your account. You can repeat these steps to block other aliases which are being used by spammers. The sending server will not be able to complete the connection to the Fastmail incoming server, since during the initial portion of the connection the destination email address is specified, and the Fastmail incoming server will reject the connection with this SMTP error code:
Code:
550 5.1.1 <sp@example.com>: Recipient address rejected: User unknown in virtual mailbox table
This is the best possible way to disable that alias, since the sending system is told that the mailbox does not exist.

Bill
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Old 15 Jul 2017, 11:03 AM   #11
n5bb
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Join Date: May 2004
Location: Irving, Texas
Posts: 8,178
Quote:
Originally Posted by camner View Post
A followup question related to writing Sieve rules. Currently my sieve rules for discarding mail to known "spammy" targets at my domain looks like this...
I would suggest that rather than use a long list of aliases you want to not accept, you just block those addresses in the aliases table as I described. If you have a large number of these, you might consider removing your wildcard delivery alias and affirmatively add the aliases you want to accept.

If you decide to continue the long sieve script, you should be able to change #1 and #2 as follows. Just add "x-delivered-to" as shown. I tested this and it seems to work correctly.
Code:
       # 1. 'matches' can contain wildcards, 'contains' cannot
         address :matches ["to","from","x-delivered-to"] 
         [
          "adobe@mydomain.com",
          "adobe1@mydomain.com",
          "adobe2@mydomain.com",
          "adbrs1@mydomain.com",
          and about 50 more!
        ],

       # 2. for partial match but cannot contain wildcards
         address :contains ["to","x-delivered-to"]
         [
          "info@mydo",
          "sales@mydo"
         ],
Bill
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Old 16 Jul 2017, 09:45 AM   #12
camner
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Posts: 545
Quote:
Originally Posted by n5bb View Post
No, that's not what I meant.
  • Go to the Settings>Aliases screen.
  • Click New Alias at the top.
  • Enter a new email address at your domain, such as sp @ yourdomain
  • Removing the Deliver to address will not prevent messages sent to that alias from being delivered to your account.
  • But you can choose a Restrict senders policy of "Reject (bounce) all mail sent to this address (disable the alias)".
  • Click Save at the top to save and exit. Click Settings>Mail to go back to your message list.
If you have a wildcard delivery alias set up for your domain, the steps above will disable a single alias at your account. You can repeat these steps to block other aliases which are being used by spammers. The sending server will not be able to complete the connection to the Fastmail incoming server, since during the initial portion of the connection the destination email address is specified, and the Fastmail incoming server will reject the connection with this SMTP error code:
Code:
550 5.1.1 <sp@example.com>: Recipient address rejected: User unknown in virtual mailbox table
This is the best possible way to disable that alias, since the sending system is told that the mailbox does not exist.

Bill
Excellent suggestion! My only question is this...a long time ago on these boards I remember reading that using the "reject" command with Sieve was undesirable because when the system sent back the message, it used the FM main username as the "From" address (or something like that...it was a long time ago!), so it was better simply to use "discard." Do I presume correctly that this new system takes care of that weakness?

My only hesitation is that with about 50 (so far!) addresses to deal with, my Sieve script allows me to put them in alphabetical order, and it looks as if on the Alias screen the email addresses are in newest to oldest order, which makes it a bit tedious to find a particular address.
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Old 16 Jul 2017, 12:03 PM   #13
BritTim
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Join Date: May 2003
Location: mostly in Thailand
Posts: 2,467
Quote:
Originally Posted by camner View Post
My only hesitation is that with about 50 (so far!) addresses to deal with, my Sieve script allows me to put them in alphabetical order, and it looks as if on the Alias screen the email addresses are in newest to oldest order, which makes it a bit tedious to find a particular address.
That is true. On the other hand, the alias solution is more robust. Anything based on sieve needs to cover several eventualities (and I notice, by the way, that you do not catch all cases where the address is in the cc header) and changes elsewhere in the sieve script might break things in the future. By the way, what do you want to happen if the message is to both one of the rejected addresses and one of your good addresses? If you still want to reject delivery, you probably need the sieve solution with all its complexity. If you want delivery to the good address to occur, your current custom sieve is broken.
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Old 16 Jul 2017, 01:37 PM   #14
n5bb
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Join Date: May 2004
Location: Irving, Texas
Posts: 8,178
Arrow User unknown alias rejection & alias sorting

Quote:
Originally Posted by camner View Post
Excellent suggestion! My only question is this...a long time ago on these boards I remember reading that using the "reject" command with Sieve was undesirable because when the system sent back the message, it used the FM main username as the "From" address (or something like that...it was a long time ago!), so it was better simply to use "discard." Do I presume correctly that this new system takes care of that weakness?
The method I described blocks at the SMTP stage, before the message is accepted. This is completely different than a sieve reject action after a message has been received. I just double-checked this by sending an email from a Gmail account to my personal domain blocked alias. The response at the Gmail account was as I described earlier (and shown below). The fastmail-owned domain I log into was nowhere in the raw message contents. This is exactly the response to any other email address which does not exist.
Code:
The response from the remote server was:
 550 5.1.1 <aa@mydomain.xxx>: Recipient address rejected: User unknown in virtual mailbox table 
Quote:
Originally Posted by camner View Post
...My only hesitation is that with about 50 (so far!) addresses to deal with, my Sieve script allows me to put them in alphabetical order, and it looks as if on the Alias screen the email addresses are in newest to oldest order, which makes it a bit tedious to find a particular address.
That is not true. The Aliases screen sorts all entries first by the domain (alphabetically), then by alias local part (alphabetically). So this would be an example of the alias display:
  • a @ fastmail.com
  • m @ fastmail.com
  • p @ fastmail.fm
  • z @ fastmail.fm
  • c @ imap.cc
  • j @ imap.cc
  • b @ mydomain
  • c @ mydomain
  • d @ mydomain
  • e @ mydomain
  • a @ warpmail.net
  • b @ warpmail.net
There is also a Search Aliases tool at the upper right. You can search for:
  • The complete email address
  • The local part (before @)
  • The domain (after @)
  • The high level domain (.com, .net, .cc)
  • The deliver to (target) address
Bill
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Old 16 Jul 2017, 02:40 PM   #15
n5bb
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Posts: 8,178
Arrow Messages sent to more than one of your addresses

Quote:
Originally Posted by BritTim View Post
...By the way, what do you want to happen if the message is to both one of the rejected addresses and one of your good addresses? If you still want to reject delivery, you probably need the sieve solution with all its complexity. If you want delivery to the good address to occur, your current custom sieve is broken.
This can get complicated.
  • If a single email is sent with several of your addresses (possibly including blocked aliases) in the To, Cc, and/or Bcc sending fields, the message is typically split into multiple messages and these are individually delivered to your account.
    • Messages sent to your account main address are by default targeted for delivery to your Inbox folder.
    • Messages sent to an alias are by default targeted for delivery as specified by the alias table entry. This is normally Inbox, but can be modified to any other folder. For example, the target could be set to username+test @ fastmail.com, and multiple internal or external targets can be used. So you could specify that three copies of all messages sent to that alias are delivered to three separate folders.
    • Sieve can change the target delivery folder, forward the message, or discard the message.
  • If the message was sent to three addresses (two normal and one you wish to block) using the To and/or Cc addressing fields, three nearly identical copies (with identical To and Cc fields as specified by the sender) are potentially delivered to your account (if none are rejected aliases).
    • One has the X-Delivered-to header set to one of the normal addresses and is delivered to the folder specified by the alias target. This can be overridden by sieve to any other folder, or sieve can block this copy of the message based on To, Cc, or X-Delivered-to.
    • The other has the X-Delivered-to header set to the other normal address and is delivered to the folder specified by that first alias target. This can be overridden by sieve to any other folder, or sieve can block this copy of the message based on To, Cc, or X-Delivered-to.
    • If there is no alias block, the third "bad" message has the X-Delivered-to header set to the address you wish to block and is delivered to the folder specified by that second alias target. Sieve can block this copy of the message based on To, Cc, or X-Delivered-to.
    • If the "bad" message is blocked by an alias marked to reject, that message is never received at your account.
    • If the "bad" address was in the To or Cc field, the two normal address copies could be blocked by sieve script which noticed the address you want to block.
    • If multiple identical copies of the same message are delivered to the same folder (or Inbox) at your account, normally only one copy will remain, and the others are discarded. This is controlled by the Duplicates setting in the Advanced settings for a folder.
    • But if the "bad" address was in the Bcc field when sent, the two normal address copies won't contain any mention of the "bad" address, so they can't be blocked. This is true no matter how you try to block the bad messages.
Bill

Last edited by n5bb : 16 Jul 2017 at 02:59 PM.
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