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The original was posted on /r/microsoft by /u/theresmorethan42 on 2023-09-15 20:26:07.

Has anyone else had success with a hosted exchange server, that previously was working fine, but after an WAN IP change is consistently going to junk for only O36 tenants?

Before you ask:

  • Yes, we have valid SPF and signed DKIM (we know this both by looking at GSuite email details, O365 detail reports, and also DMARC reports)
  • PTR record is in place and valid
  • We are not on any known blacklists (neither the IP, nor domain)
  • It only appears to affect O365, GSuite is totally happy, and so is pretty much everyone else.
  • We opened a case with MS, who ran around in circles with like 5 different “techs” who wanted to do a screen-share and had no idea what we were talking about.

We are getting hammered on this, anyone have any suggestions?