Dealing with Blocked IP

Hi ATT team,

I'm sure you're swamped, so I'm really sorry to be bothering you.

We're receiving the following message:

553 5.3.0 alph732 DNSBL:RBL 521< REDACTED >_is_blocked.For assistance forward this error to abuse_rbl@abuse-att.net

We send a weekly newsletter. It's been blocked for subscribers using @att.net, @sbcglobal.net, @bellsouth.net, @prodigy.net, etc.

I've emailed abuse_rbl@abuse-att.net each week (only once per week), following the blocks, but haven't gotten a response.

We operate a double-opt-in email newsletter, for which we have one-click unsubscribes, and have configured the SPF, DKIM, DMARC, and Reverse DNS.

We have 2 dedicated IP addresses, one since 2018 and the other since 2022.

There are currently nearly 300K subscribers.

​Could you please let us know what we need to do in order to unblock our IP?