Mail Receiving Issue

[lewismedia]

Hello,

One of the accounts on our server can't seem to receive mail from certain people. The person sending the mail has tried every email account we have created, and all return the same error:

The following recipient(s) cannot be reached:

'user@server.ca' on 11/12/2008 2:55 PM

550 5.1.1 ... User unknown

The account most definitely exists, and we can send mail to it from most other email addresses - it's just a handful of senders that can't seem to get it through.

Trouble Shooting Steps we've taken:

1) We've checked all our Exim logs and there are no records of the attempted mail delivery - it *seems* like it's not even getting to our server

2) We've double checked the DNS cache at the sender, and they have the right information (so it *should* be getting to our server)

3) We've double-checked mailbox permissions on our server

4) We've deleted and re-created the mailbox and the hosting account just ot be sure

5) We've double-checked the local and remote hosts listing on the server to make sure - and yes, it is delivering locally.

6) We've restarted Exim several times, just to be sure

We're stymied though - from the sender's end, it looks like our mail server is ditching the email, and from our end it looks like the mail is never even touching our machine.

Any suggestions/ideas would be VERY welcome

~ Joseph

[arunsv84]

Check whether the ips are blocked or not...

[lewismedia]

You mean through the firewall?

Looking into it - but would that generate a user-not-found error?

[arunsv84]

Please refer the following link...

http://www.howtoforge.com/forums/showthread.php?t=24697

Hope this helps..

[lewismedia]

Thanks, but that's unfortunatley not it either. We aren't running ISPConfig (that I know of) and I did double-check to make sure the domain was set to use the local server as the mail exchanger.

I also double checked the localdomains file, and it is listed correctly.

The weird part about this, is we don't seem to be getting any log entries about the rejections. It's as though it's getting rejected before hitting exim.

Any other hints?

[sparek-3]

Check beginning from the sending end.

What outgoing SMTP server is the sender using to send out the message?

Whatever server that user is using as their outgoing mail server may have your domain name set up on that machine and it is trying to deliver the message locally. Check to see if that is the case.

[lewismedia]

I suppose that's a possibility, but I have no way to actually test that. Their mailservers are run through megamailservers.com (I believe their provide mail & dns services to telco's and ISP's).

The people at the ISP believe everything is clean - but I have no way to actually test if it is.

I even tried contacting megamailservers.com to see if we could resolve it that way, but they have no contact details on their site, and their WHOIS information is clearly out of date as it goes to someone's personal number.

[sparek-3]

That would be my only suggestion. If its not that, then try having the user's ISP (or administrator of whatever outgoing mail server they are using) check to make sure the MX records for your domain name are being looked up correctly on their servers.

If the messages are not ever reaching your server, then the problem is not with your server and its really out of your hands.

This is why it is always best to diagnose mail sending problems, analyzing each steps that that the message should have taken, and following those steps exactly. (Did the user actually click send? What mail server did the sender send the message to? Did that server receive the message? Did they send the message out? etc.)

[lewismedia]

Sparek - thanks, I finally managed to track it down with your tip.

It turns out it was the SMTP server they are using.

For those that care, MegaMailServers.com = Hostpia (found that in another thread) and getting Hostopia's tech support on the phone helped me find out that they actually have an open hosting/mail account on their network.

So - long story short, when Rogers (the client's original hosting provider) cancelled the account, that change never made it to the Hostopia, so the SMTP servers in Hostopia's networks were still trying to deliver it locally.

Bah - what a pain. Thanks though.

Oh yeah - and if anyone else has this issue, try calling Hostopia diretly, they were supprisingly helpful.

~ Joseph