different domains perhaps?
Gmail was blocking one email address but not another, both on the same AWS domain.
Fixed that at the gmail web interface.
Looks like people have complained tot he Better Business Bureau and had their issues resolved.
I just filed a formal complaint with the BBB.
This is CENSORSHIP for them to block IPs with no advance notice and even worse with no QUICK way to remediate it. At least notify people in advance OR have a way to resolve this in 24 hours or less…
They are preventing me from emailing legitimate companies for legitimate business.
See for yourself:
https://www.bbb.org/us/ca/sunnyvale/profile/network-security/proofpoint-inc-1216-254120/complaints