Nathanael, You can reach out to me privately if you'd like. Typically those are related to DNS being unable to resolve an MX/A/AAAA for your 5321 Mail From domain, but I can take a better look to be sure.
-- Alex Brotman Sr. Engineer, Anti-Abuse & Messaging Policy Comcast > -----Original Message----- > From: NANOG <nanog-bounces+alex_brotman=comcast....@nanog.org> On > Behalf Of Nathanael Cariaga > Sent: Wednesday, May 5, 2021 2:18 PM > To: NANOG <nanog@nanog.org> > Subject: Comcast mail contact > > Anyone from Comcast on this list? would appreciate if you can reach out off > the > list. Have a few concerns regarding Comcast servers intermittently throwing > 550.5.1.0 -- invalid domain errors.
