[jayski]

hmm, I've made several attempts at this with postfix with DKIM,DMARC and SPF all correctly configured and validated and big providers will still sometimes flag me as spam.

It sounds nice in theory, in practice I've found it's pretty much impossible to send your own email reliabily.

The cheapest working fix for me is to relay everything through a AWS SES, and magically everything is now accepted. A little frustrating, but that's what the Internet has come to.

[camgunz]

I don't want this to turn into a big support thread, but I'm always surprised by this stuff. It's not like the algorithm has some case for small services like this, like Google's spam detection is heavily based on "you sent lots of messages, they're very very alike, significant numbers of users marked them as spam", because that's the actual spam problem. Source: I've worked on political campaigns. I'm not saying you did anything wrong or incorrectly, just that I'd love to know what was really going on.

[jayski]

Aside from SPF, DMARC and DKIM, there's the concept of "pre-warming" an IP.

Where you gradually send more and more email throughout a few weeks until you have enough good reputation to send your entire volume. This is the part that's outside of normal configuration and takes more time.

In my particular case I was trying to move a system that sends about 5million legitimate emails per month (notifications for a lot of customers) - off of AWS onto a self hosted solution.

We spend about 2k per month just on sending emails and I thought if I spent a few days on it we could save that money.

Unless your IPs have built a reputation it's not going to work. I could gradually migrate volume, monitor the bounce rate, adjust, etc. But that was more work than I could afford to put into that project. I also couldn't risk getting emails sent to spam while I experimented.

https://www.twilio.com/docs/sendgrid/ui/sending-email/warmin...