Our physical server godzilla forwards mails to our virtuall VMware server b4. They are on the same net. Often connection drops, we can't ping godzilla with our b4. That means mails from godzilla won't reach b4 and the mails will be in handed into the mailq. Sometimes it takes some hours and the issue will auto fix itself, b4 will wake up and the mail will be delivered. Another thing if we remotely ssh into the b4, the b4 will wake up and and receive any mailq mails from godzilla and deliver them.

netadmin@b4:/var/log$ arp -a
? (192.168.209.80) at 00:1E:C9:AE:79:9D [ether] on eth0

root@godzilla:/usr/local/bin# arp -a
? (192.168.209.20) at 00:50:56:91:7d:b2 [ether] on eth0