AnsweredAssumed Answered

Soft Bounce Error Messages: Yahoo, AOL, and Verizon

Question asked by Ande Kempf Expert on Sep 17, 2019
Latest reply on Sep 18, 2019 by Ande Kempf

Question on Soft Bounces


Context/background: Recently warmed dedicated IP. This process went very well. After warming we sent a promotional email and the deliverability is terrible (around 60%). Note: about 8 days between last warming email send and first promo email.


Problem: Majority of bounces are soft and have returned error messages for Yahoo, AOL and Verizon. The error message returned are all:

554 5.4.5 [internal] (last transfail: 421 4.7.0 [TSS04] Messages from temporarily deferred due to user complaints -; see

Other information: IP Sender Score/Reputation all looks great. IP is not listed on any blacklists (According to ReturnPath. MXtoolbox and Talos)


Question: How do you mitigate this type of soft bounce error? It seems to be the one issue we're facing.