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Why does mail not seem to be delivered despite no obvious problem in SMTP log
Question asked by Rolf Jacobs - July 17, 2015 at 10:12 AM
Unanswered
I set up (2) Smartermail servers at two separate locations.
 
mail.a.com (SM 14.x) and mail.b.net (SM 12.x)
 
We have been able to send mail between the two locations without any trouble for a couple years.
 
In the last week or so we stopped being able to successfully send mail from b.net to a.com
 
We have no problem sending from a.com to b.net.
 
Thinking that perhaps it was a problem at a.com we upgraded to 14 on a.com but it did not resolve the problem
 
a.com is with Network Solutions while b.net is with GoDaddy
 
MXtoolbox tests are typical for a.com  (no apparent problem and MX record seems normal)
 
However b.net indicates there are no MX records for b.net 
 
We have made no changes to DNS (not sure if GoDaddy or NS made changes)
 
The SMTP log below is from a test mail being sent from b.net to a.com
 
The message appears to be sent successfully but it does not make it to the users inbox in a.com.
 
[2015.07.17] 09:35:45 [b.b.b.b][58270848] rsp: 220 mail.a.com
[2015.07.17] 09:35:45 [b.b.b.b][58270848] connected at 7/17/2015 9:35:45 AM
[2015.07.17] 09:35:45 [b.b.b.b][58270848] IP in whitelist
[2015.07.17] 09:35:45 [b.b.b.b][58270848] cmd: EHLO mail.b.net
[2015.07.17] 09:35:45 [b.b.b.b][58270848] rsp: 250-mail.a.com Hello [b.b.b.b]250-SIZE250-AUTH LOGIN CRAM-MD5250-8BITMIME250 OK
[2015.07.17] 09:35:45 [b.b.b.b] [58270848] cmd: MAIL FROM:<r@b.net> SIZE=1057
[2015.07.17] 09:35:45 [b.b.b.b][58270848] rsp: 250 OK <r@b.net> Sender ok
[2015.07.17] 09:35:45 [b.b.b.b][58270848] cmd: RCPT TO:<r@a.com>
[2015.07.17] 09:35:45 [b.b.b.b][58270848] rsp: 250 OK <r@a.com> Recipient ok
[2015.07.17] 09:35:45 [b.b.b.b][58270848] cmd: DATA
[2015.07.17] 09:35:45 [b.b.b.b][58270848] rsp: 354 Start mail input; end with <CRLF>.<CRLF>
[2015.07.17] 09:35:45 [b.b.b.b][58270848] rsp: 250 OK
[2015.07.17] 09:35:45 [b.b.b.b][58270848] Data transfer succeeded, writing mail to 47425896166.eml
[2015.07.17] 09:35:45 [b.b.b.b][58270848] cmd: QUIT
[2015.07.17] 09:35:45 [b.b.b.b][58270848] rsp: 221 Service closing transmission channel
[2015.07.17] 09:35:45 [b.b.b.b][58270848] disconnected at 7/17/2015 9:35:45 AM
 
Any thoughts, or direction on further investigation?

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Rolf Jacobs Replied
July 17, 2015 at 11:10 AM
UPDATE!  I just noticed that when sending mail from another domain (z.com) on the mail server at location B, mail is delivered to user@a.com as expected.
 
So why then is mail sent from b.net at location B not delivered to the same user@a.com?
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SpamHurts Replied
July 17, 2015 at 7:24 PM
This is just a guess. Some things in your question do not really matter, like the registrars. We use an outgoing gateway, so external delivery is obvious in my logs. The seems like local delivery to me. 

Did you at one time have a,com set up on the same server as bnet? If so, when b.net sends to a.com, it will do local delivery, and not use dns to deliver to the new physical server. The b.net server thinks that the a.com user is on the same box, so it just puts the message in that box. IF you do search the domains on  the b.net server, and see the a.com domain there, you will see the messages you tried to send in that account. This is just a guess.
 
Now you will have another issue too. If b.net has no mx record, then it should not get external email at all. That is the part of your question that doesn't make sense. You state you have no issues sending email from a.com to b.net. And z.com being hosted on the b.net server and sending to a.com doesn't make sense either. 
 
And wait a tick what does the delivery log look like for the z.com sending to a.com?
what did the delivery log on the a.com server show, did the b.net email hit it and get rejected because of spam or content filter. What did the SMTP log say for b.net to a.com? And look at the smtp on server b for the z.com delivery.
 
And in the future, on the a.com server... a message not being in the inbox doesn't mean it didn't deliver, check your logs, and check em again!! :)
Remember kids, every time a spam message gets blocked, a nerd gets their glasses. spamhurts/July 15

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