Exchange not receiving email from certain domains

[mojo1979]

Hi,

Over the past week, I have had four domains that are unable to send email to my domain. I can recieve email from everyother domain apart from these four, which happen to be my largest clients.

Everything looks 'normal', I am not blocking their domains, my spam filters are ok, and the client can nslookup my exchange fine.

They are saying when the connection hits my exchange, it is dropped, but I can't see any occurrence of that.

Anybody have any ideas?

Thanks!Steven

 

[paella33]

Any firewall in between?

 

[mojo1979]

Yep, I have a Cisco Pix, but nothing has been changed on it for over 6 months...

 

[N0ktar]

Are they getting NDRs? Have them forward you the exact error messages to an external email account and look for specific error numbers.

 

[mojo1979]

Resolved, just reset the firewall and it started working...