IS there any reason my Hub transport server queues get full of emails that I'm not sending? Eventually the emails are dropped but I can have over 100 or these in a few days and if I remove them, with in a few days more will return. The Error message says "451 4.4.0 Primary target IP address responded with: 421 4.2.1 unable to connect. Attempted failover to alternate host, but did not succeed. Either there is no alternate host or delivery failed to alternate host." See attached pic.
I have used telnet to verify that I have no open relays and I also used mxtoolbox to also confirm I have no open relays. I believe this is just spam, but just trying to understand why does it seem like it's being sent from my server. This is one of the undelivered properties:
Subject: Undeliverable: Tasty drink shreds extra fat
Internet Message ID: <0d77219b-56f6-4aeb-b182-c
From Address: <>
Size (KB): 16
Message Source Name: DSN
Source IP: 255.255.255.255
Date Received: 12/30/2015 1:21:50 PM
Expiration Time: 1/1/2016 1:21:50 PM
Last Error: 400 4.4.7 Message delayed
Queue ID: MAIL\28211
2;2;400 4.4.7 Message delayed;0;CN=Outbound Public Connector,CN=Connections,C
Routing Group (DWBGZMFD01QNBJR),CN=Routi
ng Groups,CN=Exchange Administrative Group (FYDIBOHF23SPDLT),CN=Admin
I believe this mail is being caught and rejected by my Hub Transport Anti-spam. I have enabled Exchange's HT anti-spam features. Any advice would be appreciated.