Mailbox problem

Hello All,

Today I have encountered a very strange problem in mail settings via Cpanel.

I have set up a new mail address [ jobs@domain.com ] , and set up also 2 forwarders for that account .
I also accesses the webmail to be sure it exists and in fact - I even successfully sent outgoing mail from that address.

This is a normal procedure that I have done many times before...
This time though, something really strange came up.

When I am sending mail to that account [ jobs@domain.com ] , I get a

Code:

 550 "Unknown User"

mail back ( from postmaster ) but the strangest part is - that at the same moment, I also get the forwarded mail to the correct forwarded address .

My question is - how is it possible that the server return

Code:

 550 "Unknown User"

and at the same time knows to manage the forwarding of a supposedly non existing account ?? - What can be the problem ? and how to fix it ? ( I assume that some will suggest to delete the account and set up a new one - but that would not really help to find the CAUSE for such a problem or to ensure it does not happen again .. )

 

Thank you for your reply.

Right now , I do not have access to the server , But as for the MX recods for the domain - I assume that they are correct because I have about 40 other accounts on that same domain that works just fine .

 

I have now accessed the server , and as per your suggestion, the /var/log/exim_mainlog has the following :

Code:

2014-07-27 03:46:02 pid 3023: SIGHUP received: re-exec daemon
2014-07-27 03:46:02 cwd=/var/spool/exim 3 args: /usr/sbin/exim -bd -q1h
2014-07-27 03:46:02 exim 4.82 daemon started: pid=3023, -q1h, listening for SMTP on port 25 (IPv6 and IPv4) port 587 (IPv6 and IPv4) and for SMTPS on port 465 (IPv6 and IPv4)
2014-07-27 03:46:02 cwd=/var/spool/exim 2 args: /usr/sbin/exim -q
2014-07-27 03:46:02 Start queue run: pid=28580
2014-07-27 03:46:02 1XAu5t-0004bj-Ko Message is frozen
2014-07-27 03:46:02 1XAu6t-0004fa-06 Message is frozen
2014-07-27 03:46:02 1XAu6t-0004fi-Gm Message is frozen
2014-07-27 03:46:02 1XAu6t-0004ft-Ru Message is frozen
2014-07-27 03:46:02 1XAu5t-0004be-E2 Message is frozen
2014-07-27 03:46:02 1XAu6t-0004fq-Ps Message is frozen
2014-07-27 03:46:02 1XAu6t-0004fm-N0 Message is frozen
2014-07-27 03:46:02 1XAu5v-0004cX-2Q Message is frozen
2014-07-27 03:46:02 1XAu5v-0004cf-OI Message is frozen
2014-07-27 03:46:02 1XAu5v-0004ch-Pb Message is frozen
2014-07-27 03:46:02 1XAxqK-00075q-SS Message is frozen
2014-07-27 03:46:02 1XAxqK-00075a-D6 Message is frozen

...... many more just the same ....

I have also tried and verified that the same problem exists also for NEW mailboxes on the same domain [ Old mailboxes work as expected ..]

What I have learned about the situation so far :

1 . The mailbox exists and is configured correctly .
2 . One can access the webmail inbox.
3 . One can successfully send outgoing mail from said webmail
4 . One can NOT login using a regular mail client [ Tried Mozilla thunderbird , Android Clients, iPhone Clients - All with normal pop/smtp/imap ports AND ssl ..] - The error is [ "Authentication failed" ]
5 . One can NOT send mails to said account , the immediate reply is [ 550 "Unknown User" ]
6 . One can successfully send outgoing mail using this mailbox with regular mail client but with different SMTP account on same domain ( info@mydomain.com )

What I have tried so far ( in no particular order ):

1 . In WHM -> Restart all mail related services , as well as a graceful server reboot.
2 . In WHM -> Mail Delivery Report -> Report inquiery for mailbox with [ no records found result ]
3. In WHM -> Mail troubleshooter - No problems found
4. In WHM -> Repair mailbox permissions - NADA
5. In WHM -> MX entry - Verified Routing for mydomain.com - Local mail exchanger, TTL 14400, priority 0 domain mydomain.com
6. In WHM -> Mail Queue manager - some "frozen" but none has to do with the specific problematic mailbox .
7. In Cpanel -> Verified MX entry
8 . In Cpanel -> DELETED all forwarders for the specific mailbox and eventually for the WHOLE DOMAIN .
9 . In Cpanel -> DELETED the whole mailbox and created [ several ] New one.
10 . In Cpanel -> Mail authentication -> DKIM I tried both enabled AND disabled
11 . In Cpanel -> SpamAssassin AND boxtrapper are currently disabled.
12 . No quota problems, mail or disk or otherwise.

None of the above helped ...

This problem is becoming urgent , And I am really at the dark here ...