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Could this be IPv6-related? I've run my own server for a long time, but when I spun up a new VPS and enabled IPv6, I suddenly couldn't send mail to Comcast cust

Could this be IPv6-related? I've run my own server for a long time, but when I spun up a new VPS and enabled IPv6, I suddenly couldn't send mail to Comcast customers. It seems that the single default IPv6 address fell into a privately-blacklisted /64. I was able to work around it by firewalling Comcast's IPv6 MX hosts, but getting my own /64 was the real fix. On the other hand, I don't know anyone with an @some-microsoft-property email address, so I don't know whether I'll be having trouble sending things there. I can reach Gmail and Yahoo (and after getting my own /64, Comcast) without trouble, though. EDIT: Hmmm, mail-test.com seems to be a parked domain.

cornedor 10y ago
A college of my has struggled days with this issue, gmail wouldn't accept any mail send from a IPv6, ended up disabling IPv6 at the end. It seems like google only uses IPv6 for internal mail's, sending a mail to another account sends them using IPv4. Even Facebook, Microsoft etc still use IPv4 for their email's.
- dingaling 10y ago
  Google do of course use IPv6 externally, but require rDNS for all inbound IPv6 SMTP sessions. Without that set for your MTA's host they'll reject immediately.
tudorw 10y ago
thanks for the thought, I'll check but pretty sure I', stil on IPv4, 6 not enabled, maybe I'll try enabling it, or burning some sort of effigy, http://www.mail-tester.com/ http://www.mail-tester.com/ is the link I intended.
- tudorw 10y ago
  Okay, jumped some hoops for m$ to try and get my email working, but no joy, sender.office.com reports the IP is not blocked and suggests I refer to bounce error (there is no bounced message), I tried the Outlook mitigation route, and after 24 hours received a "Not qualified for mitigation ... Our investigation has determined that the above IP(s) do not qualify for mitigation." message (my stars). Today I've joined the Microsoft Smart Network Data service, and that reports the IP of the mailserver as having normal service, so where now ? PM Bill?

cornedor 10y ago

A college of my has struggled days with this issue, gmail wouldn't accept any mail send from a IPv6, ended up disabling IPv6 at the end. It seems like google only uses IPv6 for internal mail's, sending a mail to another account sends them using IPv4. Even Facebook, Microsoft etc still use IPv4 for their email's.

dingaling 10y ago
Google do of course use IPv6 externally, but require rDNS for all inbound IPv6 SMTP sessions. Without that set for your MTA's host they'll reject immediately.

tudorw 10y ago

thanks for the thought, I'll check but pretty sure I', stil on IPv4, 6 not enabled, maybe I'll try enabling it, or burning some sort of effigy, http://www.mail-tester.com/ http://www.mail-tester.com/ is the link I intended.

tudorw 10y ago
Okay, jumped some hoops for m$ to try and get my email working, but no joy, sender.office.com reports the IP is not blocked and suggests I refer to bounce error (there is no bounced message), I tried the Outlook mitigation route, and after 24 hours received a "Not qualified for mitigation ... Our investigation has determined that the above IP(s) do not qualify for mitigation." message (my stars). Today I've joined the Microsoft Smart Network Data service, and that reports the IP of the mailserver as having normal service, so where now ? PM Bill?