[cobalt-users] [RaQ4] SMTP not responding

["Harry Mueller" <hmueller@xxxxxxxxxxxx>]

Greetings all,

Today my users started having problems sending mail via SMTP.  When the mail client tries to 
send an email message the SMTP connection never opens.

The day started with a large number of messages not being sent and the following error 
returned:

   ----- The following addresses had permanent fatal errors -----
<solutions@xxxxxxxxxxxxx>

   ----- Transcript of session follows -----
550 5.1.2 <solutions@xxxxxxxxxxxxx>... Host unknown (Name server: earthlink.net: no data 
known)

This persisted for a couple of hours until I rebooted the machine and after that the SMTP 
stopped responding.

POP & IMAP work OK and mail sent through the webmail interface goes out fine but mail clients 
still don't work.

I have rebooted several times, tried clients inside and outside my local network, different 
platforms, different clients, all with no luck.

I'm stumped, any ideas?

Thanks,
  Harry