Our ISP appears to have been blacklisted so we have configured the server to send mail using the Dyndns mailhop service to relay emails.
This usually works on an Exchange 2003 server, but doesn't seem to be having any effect on an Exchange 2007 server.
Is this a known issue, or am I doing something obviously wrong?
Thanks for your help!
asked Jan 19 '12 at 12:08 PM in Dyn Email
With so little information given we are reduced to guessing.
Dyn Standard SMTP (old Mailhop Outbound) doesn't care who is sending email through it as long as the sender can authenticate and is using an accepted port (and hasn't used up their daily quota).
If you are trying to send using port 25, your ISP may be blocking that port (quite common), or even one of the common alternatives.
See this link for alternate ports.
answered Jan 19 '12 at 04:36 PM