I was having trouble last week getting a new exchange server to receive email (which turned out to be an incorrect MX record that the host put in).
As of today, I can receive email fine, but oddly enough, now I can't send anything (I was able to last week when I couldn't receive).
In the time between last week and this week the only thing I changed was the SSL certificate (I didn't realize that I needed a few domain variations, and I didn't have mail.domain.com, so I had one reissued with what I needed).
I then changed the EHLO response on my send and receive connectors to be mail.domain.com from the pop.domain.com and smtp.domain.com that they were before.
When I put the new certificate in, exchange told me that there was an old certificate bound to SMTP, and asked if I would like to replace it with the new one, which I said yes to.
Any ideas what could be going on?