On 2026-01-24 at 10:35 +0100, Klaus Ethgen via mailop wrote: > Hi folks, > > I need to use a m365 Outlook mailbox that is a whole pain in the a... > However, I managed to forward all mails to my personal mailserver > that supports proper filtering and functional imap. > > The problem occurs when mails from different m365 accounts or even > teams get forwarded. My mailserver rejects them as the SPF is usually > not valid for them. > > So the question I have is why microsoft is not capable to just > implement working and correct mail forward. They are not capable to > even forward their own mails propper. > (...)
This is the reverse of the more common "I forward my mail to $BigMailer but it gets marked as spam for passing SPF!" (which is completely expected for forwarded mail) I am firmly convinced that if you forward your email from A to B, then *you* should let B know that it is to expect forwarded mail from A, so it doesn't misinterpret it exactly that way. Which is often hard because then B turns out to be $BigCompanyFreemail and they doen't allow such option (yet the blame goes into A). In your case, this is much easier, since you control de mail server. A being m365, it doesn't seem simple/desirable to whitelisting all their sending IP addresses, specially as that would also whitelist mail from any other m365 customer. There may be headers showing that it was forwarded from your m365 account which could be used to discern those cases, but there is an even easier solution. Use a unique address for the forwarding, e.g. [email protected] Then *exempt* it from filtering. You should also configure it so that spam rules treat O365 servers as within your network for ip reputation, disallow bounces, etc. I'm not sure if Microsoft 365 would, in some cases, leak to the sender the email address you are forwarding to. I would pessimistically assume that in some scenarios it would do so. But if the secret address got into a spam list, you would only need to switch to a new one and treat the old address as a 100% spam source. Regards _______________________________________________ mailop mailing list [email protected] https://list.mailop.org/listinfo/mailop
