So I have a weird one.  I have a client who has been with us a long time,  There is a single user that is having a problem sending to a specific remote email address.  If other users from the same domain send to the same remote user, then there are no issues.  

 

What is happening is the my local user creates an email, adds an attachment (not that this matters, we tried both ways), and send to the intended remote recipient.  

 

The local SmarterMail15 server is responding to the local sender "No Such User Here"

 

This makes so sense.  

 

This is what it looks like in the logs:

 

[2018.06.06] 08:56:20 [99.99.99.99][28464718] rsp: 220 mail.myserver.com
[2018.06.06] 08:56:20 [99.99.99.99][28464718] connected at 6/6/2018 8:56:20 AM
[2018.06.06] 08:56:20 [99.99.99.99][28464718] cmd: EHLO NP2719
[2018.06.06] 08:56:20 [99.99.99.99][28464718] rsp: 250-mail.myserver.com Hello [99.99.99.99]250-SIZE 31457280250-AUTH LOGIN CRAM-MD5250-STARTTLS250-8BITMIME250 OK
[2018.06.06] 08:56:20 [99.99.99.99][28464718] cmd: STARTTLS
[2018.06.06] 08:56:20 [99.99.99.99][28464718] rsp: 220 Start TLS negotiation
[2018.06.06] 08:56:20 [99.99.99.99][28464718] cmd: HELO NP2719
[2018.06.06] 08:56:20 [99.99.99.99][28464718] rsp: 250 mail.myserver.com Hello [99.99.99.99]
[2018.06.06] 08:56:20 [99.99.99.99][28464718] cmd: MAIL FROM: <localuser@onsmartermailserver.x>
[2018.06.06] 08:56:20 [99.99.99.99][28464718] rsp: 250 OK <localuser@onsmartermailserver.x> Sender ok
[2018.06.06] 08:56:20 [99.99.99.99][28464718] cmd: RCPT TO: <remoteuser@remotedomain.com>
[2018.06.06] 08:56:20 [99.99.99.99][28464718] rsp: 550 <remoteuser@remotedomain.com> No such user here
[2018.06.06] 08:56:24 [99.99.99.99][28464718] cmd: QUIT
[2018.06.06] 08:56:24 [99.99.99.99][28464718] rsp: 221 Service closing transmission channel
[2018.06.06] 08:56:24 [99.99.99.99][28464718] disconnected at 6/6/2018 8:56:24 AM

 

 

Anyone have any idea how to track this down?  I cannot find it in the logs anywhere where this is failing DNS or anything.  

 

Thank you!