Not Receiving Email From Just Two Clients

[JiggyPoo]

I'm running Domino 6.5; I have two customers who are unable to send me email. I am able to send them email successfully. I am also able to cause one of the client's email server to reply to me by sending an email to a false email address. I've checked my firewall for banning. Banning isn't turned on. No bans in the Domino server. I'm baffled. Any ideas out there that could point me in a right direction?

Also, I've cheked w/ my ISP, too. They are not doing any mail routing or port/ip blocking.

 

[Mike2287]

Check your SMTP Inbound Controls. If Verify Connecting Host Name in DNS is Enabled this could cause your problem.

 

[JiggyPoo]

Thanks for the suggestion. This option is disabled and has been for a while on our server.

It is strange. The client attempts to telnet from their smtp server to our mail server and it simply times out. Very odd. Any other thoughts?

Also, thanks very much for such a quick reply.