Forwarding mail from a custom domain using postfix fail with outlook

Okay so where to start…

I configured postfix on my debian server to forward mail sent to * to a gmail address and it’s working !! yay ! But… it seems that every classic mail service can send mail (google, yahoo, etc) except outlook… every time I send an email from an outlook address to for example I get a 550-5.7.1 error in outlook…

Some details, I’m using cloud flare so I had to do a wonky thing in it to forward properly my mail, but I don’t think that’s the reason for outlook failing to send a simple mail…

Why something so simple can be complicated like this…

After two days searching around for an answer I think here is the place to find answers… I hope.

Thanks, Maxime


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This will mostly fail. Most of the emails you forward will violate SPF/DMARC by coming from your server. Additionally, you’ll end up forwarding spam and the recipient services will block your droplet IP as a result.

For some reason this article has some weird spacing issues that it didn’t have before, but it’s one that I used to recommend as a good read a few years ago:

You can somewhat fix this by implementing SRS, but not all recipient services (not even the major ones) care about SRS, and it still won’t stop them from holding your droplet IP accountable for any/all forwarded spam.

The bottom line is that the fight against spammers has caused email to no longer be the simple thing that it was several years ago. By my estimation, everything changed after Yahoo adopted DMARC in late 2013. Soon after, most other services adopted what some might call “militant” policies to deal with inbound spam.