I am a postmaster for a dedicated server with a newly assigned IP address on February 23, 2020. Ever since, emails originating from our IP are being blocked on att.net domains. This, despite a stellar record of activity from all domains hosted on our shared server when it was on another IP that att.net never had blocked. We have attempted daily over the course of an entire week to reach the postmaster at att.net as per instructions in emails blocked for our IP. We get an autoresponse, but no human interaction at all.
Bounce messages read like so:
host ff-ip4-mx-vip1.prodigy.net [18.104.22.168]
SMTP error from remote mail server after MAIL FROM:<[email scrubbed]>:
553 5.3.0 flpd575 DNSBL:ATTRBL 521< x.x.x.x >_is_blocked.For assistance forward this error to firstname.lastname@example.org
I would truly appreciate if an ATT postmaster support person would respond. We are growing desperate, as our IP is on zero public RBLs, and we run a properly configured server with all the necessary DNS attributions. We do not send bulk email of any type. Our clients have grown impatient, and rightfully so. This is ridiculous!