We have just installed a new exchange server into our domain, moved all the mailboxes to the new server and then changed the IP address of the old server so that we could move the new servers ip into place for a clean swap over (IP wise)

When we do this only about half of the external mail sent to the server is passed to the mailboxes however if we place the old server back on the IP address it relays all the mail to the new server.

All SMTP Connection and relay settings are the same.

Can any one think of a reason for this strange response?


Have you checked the size of the new exchange servers information store IE is it the same as the old one?

As all the mailboxes have been migrated across to the new server the old server is empty.

The mail store on the new server is at 13Gb

Running tests from my personal E-Mail account and from a Google Mail account.
It looks like the Mail is getting blocked if i add multiple recipients (2+),
If only one recipient is added the mail is delivered.

Then the mail with multiple recipients is delivered only after the old mail server is placed back into place (IP) and starts relaying the mail.