Soft Bounce - Received too many messages from new or untrusted IP
I've been monitoring our email bounces, and for one of our most recent email sends, we had a large number of bounces with the bounce reason:
554 5.4.7 [internal] (last transfail: 451 4.7.1 Received too many messages from a new or untrusted IP
We are on a dedicated IP and have been for over a year and a half, so our IP isn't new, and I haven't seen this code before on our other reports. Has anyone else seen this creep up on their end?
There were a few companies that appeared more than others, so my thought is that maybe they changed some of their internal settings, but I can't seem to understand why we saw a 300% increase in bounces.
Any insights are greatly appreciated.