[jhollington]

Bill has got most of the key points, but there are probably a couple of things I can add...

Firstly, the fact that the DSN ("bounce back") is originating at comcast.net means that the messages are not reaching Freehostia. Comcast is trying to send those messages, but they're basically not getting through for whatever reason — either they can't contact Freehostia's servers at all, or Freehostia's servers are refusing the messages outright (at the SMTP session level).

Unfortunately, without seeing the actual SMTP diagnostic code (Comcast's DSNs appear to be very unhelpful here), it's very difficult to know for certain what is happening. What you need to look for (in case it actually is there and it just hasn't ended up in the bits you've shared with us) is an error code that's usually a three-digit number starting with either a "4" or a "5" .... A "400" series error code usually means a temporary failure, while a "500" series code means a permanent failure.

Also, for a single email sent from a Comcast account, usually 3 "temporary error" DSN's are received before the "permanent error" is finally received (about 48 hours afterwards) and all of them have that very short message as the body with no extra info - just change the word from "permanent" to "temporary" for 3 prior DSN's before the permanent error one.

From this description, it looks like you're actually getting 400 series errors.... Comcast is trying to deliver the message for 48 hours, meeting repeated failures in doing so, and then finally deciding to give up with a permanent failure once the message has been in the queue for too long. While the exact timeouts differ, this is standard behaviour for most SMTP servers.

Again, though, without seeing the actual error code response, it's very difficult, if not impossible, to know for certain what is happening. If I had to guess — and it's only an educated guess based on my experience — I'd lean toward it being a DNS/SMTP/routing problem on Comcast's end. I realize you haven't changed any of your DNS records, but that doesn't mean that Comcast hasn't suddenly decided to apply a more stringent policy in checking DNS records, or that something else may not have changed on their end in terms of how DNS records are handled by their outgoing SMTP servers.

Most temporary failures are related to DNS lookup, SMTP session failures, or other Internet routing problems — essentially, and inability to actually get through to the recipient server. It's much more rare for a receiving server to refuse to accept a message with a 400-series (temporary) error, as it usually pretty much knows whether it's going to be able to deliver the message or not.

Originally Posted by n5bb

The message was sent through Comcast outgoing servers, so you need to play by their rules to reduce outgoing spam. Residential phone/cable email providers are very worried about spam being sent through their systems (for good reasons).

I'm going to assume that you can actually send messages through your Comcast servers to any other addresses? It's only your own domain that's not working?

You are sending with a non-Comcast From address through their outgoing SMTP server. This might be the cause of the error.

This could most definitely be part of the problem. In the very least it might be affecting the DSNs that you're getting, since Comcast will attempt to send those back to the original address.

I realize that you say other family members and friends can't send to you from Comcast either, and I"m going to assume that they're using their Comcast.net addresses, but I'd still recommend testing this from your actual Comcast.net address rather than your custom domain address, just to eliminate this as a possible issue and see if you can get more information out of the DSNs.

72.167.238.32 | WARNING: The hostname in the SMTP greeting does not match the reverse DNS (PTR) record for your mail server. This probably won't cause any harm, but may be a technical violation of RFC5321

While it's correct that "this probably won't cause any harm" it's not impossible for Comcast to decide to get cranky about this and refuse to deliver mail if these two values don't match. It wouldn't be the first time I've encountered this problem, albeit I think it would be the first time I've ever seen a major ISP be this picky.

Sadly, this would be Freehostia's problem to fix. There's really not anything you can do about it.

You also note that Freehostia and 50webs are owned by the same parent company. Their servers also appear to be on the same general subnet, so it's wouldn't be surprising that any routing issues that Comcast has with 50webs might also exist with Freehostia. They're not the exact same servers, but they're close enough, and a traceroute shows the same path to both — I suspect they're on the same network, basically, and if Comcast is having a problem reaching that network, it's going to have the just as much of a problem reaching Freehostia*as it does 50webs.

To be me this points more to a routing problem, which would definitely result in a temporary failure —*usually a "421" SMTP error indicating that the server is simply unreachable during the connection phase.

Of course, it's equally possible that since Freehostia and 50webs are run by the same company, they're both running similar mail service and have something going on that's blocking Comcast emails in the same way.

Your destination email address domain (and full published DNS records) look fine to me. I think that Comcast support hasn't really tried sending a message through their server to your domain. They need to actually send a message and look at their server logs. It is very strange that the DSN message says "Diagnostic-Code: smtp;", but there is no actual code. This looks like an abnormal block in their system to me, not a normal SMTP error.

I'd agree with that one as well. Other than that PTR mismatch on the SMTP header, which really shouldn't be an issue (and I'd think should result in a permanent failure, not a temporary one), everything looks fine. I even ran your domain through CheckTLS.com and the SSL/TLS setup on their SMTP servers looks completely okay.

There should really be an error message there, and in the very least perhaps you could ask Comcast to tell you what the error message is, or put you through to somebody who can (I realize first-level support types at most ISPs are often clueless about such things).