Email stops flowing after changing NIC

For some reason, messages are no longer delivered after switching out a virtual NIC on an Exchange 2013 mail server.

In the TransportRoles\Logs\FrontEnd\ProtocolLog\Smtp Send log, I'm seeing the following:

421 4.4.1 Connection Timed out

In the TransportRoles\Logs\FrontEnd\ProtocolLog\SmtpReceive
I'm seeing 250 2.6.0 Queued mail, then 221 2.0.0 Service closing transmission channel

In the Hub SMTP receive log, I'm seeing 451 4.7.0 Timeout waiting for client input

Any ideas?

Thanks,