What is a "hard" email bounce?

**JeffK** · 25 Jun 2005, 10:15 PM

I'm wondering if forum members can help me understand what constitutes a hard bounce for email.

Specifically, domains hosted at www.mydomain.com can have an address forwarded to itself eg xxxyyy@a_mail_domain.com forwards to xxxyyy@a_mail_domain.com. Mail sent to that address is returned as undeliverable. Would that be a hard bounce?

Does to return to sender function available using zoneedit.com mail forwarding send a hard bounce?

Any clues would be appreciated.

Thanks, Jeff

miley · 26 Jun 2005, 01:03 AM

There are varying definitions depending who you talk to. Email has the concept of "permanent" and "temporary" errors. Think of temporary errors (codes in the 400s) as equivalent to a telephone busy signal -- the server is saying, please try again in a little bit. A permanent error is the equivalent of the telephone doing the 3-proned tone (in the US at least) followed by the recording 'we're sorry, your call could not be completed as dialed.' The receving server is effectively saying that it will not accept this mail, so don't try again.

However, some folks (most likely the high-volume email deployers) like to think about some "permanent" errors being not so permanent. For instance, if a user is at the storage quota allowed, the mail server will give a permanent error. The user may eventually login and clear the quota problem -- and that could happen in seconds, min, days, or never, and the "permanent" problem will go away. Thus, some folks call this a soft bounce.

A hard bounce then would be something that is most likely to last for a much longer period. For instance, if an account doesn't exist, it's unlikely to come into existance for the person you are trying to reach for a very long period. Thus, some folks call it a hard bounce.

Other types of hard bounces would be policy reasons -- the email doesn't follow the standard, the receiver thinks the message is spam, the receiver is set up specially to only accept mail from certain senders, etc. These are also unlikely to change anytim soon.

From the providers point of view, the difference probably doesn't exist. If a user is at the quota, its probably unlikely that the user is going to login any time soon to clear it -- if the user was logging in frequently, she probably wouldn't be at the quota level in the first place!

Last thing -- rejection versus bounce. Once a email server has accepted the message, it takes responsibility for notifying the sender if the message is not accepted at the next hop. Thus, the receiving server only sends a bounce message if it accepts the message for some reason, then later decides/figures out that it is not deliverable. For this reason, email servers generally like to reject messages rather than accept and bounce (though there are certainly many cases where they will accept and bounce). I've mostly describe rejections above, which result in bounce message sent by the sender.

teacher · 26 Jun 2005, 06:53 PM

I thought that hard bounce uses multiple relays to the master server ...

**JeffK** · 26 Jun 2005, 06:55 PM

Hello teacher. Haven't seen you on the forum for a while.

Jeff

teacher · 26 Jun 2005, 06:58 PM

Been busy with work, publication and divorce after twenty two years of marriage!

Happy chappy now!!!!!

Hello, all

25 Jun 2005, 10:15 PM	#1
JeffK Moderator Join Date: Feb 2002 Location: Kingaroy, AU Posts: 3,179	What is a "hard" email bounce? I'm wondering if forum members can help me understand what constitutes a hard bounce for email. Specifically, domains hosted at www.mydomain.com can have an address forwarded to itself eg xxxyyy@a_mail_domain.com forwards to xxxyyy@a_mail_domain.com. Mail sent to that address is returned as undeliverable. Would that be a hard bounce? Does to return to sender function available using zoneedit.com mail forwarding send a hard bounce? Any clues would be appreciated. Thanks, Jeff

26 Jun 2005, 01:03 AM	#2
miley Essential Contributor Join Date: May 2004 Location: California Posts: 307	There are varying definitions depending who you talk to. Email has the concept of "permanent" and "temporary" errors. Think of temporary errors (codes in the 400s) as equivalent to a telephone busy signal -- the server is saying, please try again in a little bit. A permanent error is the equivalent of the telephone doing the 3-proned tone (in the US at least) followed by the recording 'we're sorry, your call could not be completed as dialed.' The receving server is effectively saying that it will not accept this mail, so don't try again. However, some folks (most likely the high-volume email deployers) like to think about some "permanent" errors being not so permanent. For instance, if a user is at the storage quota allowed, the mail server will give a permanent error. The user may eventually login and clear the quota problem -- and that could happen in seconds, min, days, or never, and the "permanent" problem will go away. Thus, some folks call this a soft bounce. A hard bounce then would be something that is most likely to last for a much longer period. For instance, if an account doesn't exist, it's unlikely to come into existance for the person you are trying to reach for a very long period. Thus, some folks call it a hard bounce. Other types of hard bounces would be policy reasons -- the email doesn't follow the standard, the receiver thinks the message is spam, the receiver is set up specially to only accept mail from certain senders, etc. These are also unlikely to change anytim soon. From the providers point of view, the difference probably doesn't exist. If a user is at the quota, its probably unlikely that the user is going to login any time soon to clear it -- if the user was logging in frequently, she probably wouldn't be at the quota level in the first place! Last thing -- rejection versus bounce. Once a email server has accepted the message, it takes responsibility for notifying the sender if the message is not accepted at the next hop. Thus, the receiving server only sends a bounce message if it accepts the message for some reason, then later decides/figures out that it is not deliverable. For this reason, email servers generally like to reject messages rather than accept and bounce (though there are certainly many cases where they will accept and bounce). I've mostly describe rejections above, which result in bounce message sent by the sender.

26 Jun 2005, 06:53 PM	#3
teacher Master of the @ Join Date: Feb 2003 Location: UK Posts: 1,167	I thought that hard bounce uses multiple relays to the master server ...

26 Jun 2005, 06:55 PM	#4
JeffK Moderator Join Date: Feb 2002 Location: Kingaroy, AU Posts: 3,179	Hello teacher. Haven't seen you on the forum for a while. Jeff

26 Jun 2005, 06:58 PM	#5
teacher Master of the @ Join Date: Feb 2003 Location: UK Posts: 1,167	Been busy with work, publication and divorce after twenty two years of marriage! Happy chappy now!!!!! Hello, all