RBL's down

As of 2025-06-24 0105Z there are 55 RBLs Offline, including some major players like barracudacentral.org.

Not seeing a mass outage here...
https://multirbl.valli.org/

PS I haven't used Barracuda since they did the whole E-mail Reg whitelist protection racket:
https://community.spiceworks.com/t/emailreg-org-a-scam-shame-on-you-barracuda/116005

Odd that's where I was seeing the problem @ multirbl.valli.org/lookup/

I'm seeing a weird problem, all emails going thru SMTP2Go aren't being received.

I can send from one of our domain accounts to Gmail and it's received at Gmail, but another isn't.
Both on the same server.

Gmail really clamped down a few months back -- I see denials from one domain, consistently. Have you enabled ARC headers?

Enabled OpenDKIM as a milter for outgoing.

First I'm hearing about OpenARC for Incoming.

Looks like OpenDKIM already supports ARC.

This is how we have been configuring Postfix.

https://starburst.help/control-web-panel-cwp/control-web-panel-cwp-admin-tutorials/dkim-not-working-on-almalinux-9-with-cwp/