UPDATE 3:15PM EST: AT&T has reported that each of the new outbound IPs has been removed from their block list.  At this time, all email sent from our Hosted Exchange platform to AT&T-hosted recipients should be relaying as normal.

 

During our process of improving email flow and performance for our customers, we have introduced a couple of new nodes to our outbound spam filter system.  As these nodes are brand new, they have limited reputations with other email providers.  The nodes are introduced gradually with minimal initial traffic to help build up their reputation.  Unfortunately it does appear that AT&T’s networks have blocked the new nodes by default.  As a result, a few users are seeing bounces when sending to recipients hosts by AT&T.

We have sent a request to AT&T to remove the blocks for our new nodes.  AT&T typically honors these requests in a fairly timely manner, so we anticipate the blocks to be removed within the same day.