We had an issue late yesterday and early today where Comcast had one or more McAfee IPs on their blacklist. Our operations team was able to work with Comcast to get those removed, and everything should be working fine now. Those errors are temp-fails, so the messages will be retried for up to 5 days.
Have a great day!
We are still seeing this issue with Time Warner. More specifically roadrunner.com and maine.rr.com addresses.
2014-01-29 13:17:52 EST Recipient Disposition: [250 Queue (RCPT Domain roadrunner.com, Message Domain maineea.org); Mode: ; Queued: yes; Frontend TLS: yes] 2014-01-29 13:18:02 EST Detail: first attempt failure: 451 all mx servers are unavailable for domain roadrunner.com