z3bra

Congratulations! A mail server is quite demanding in terms of initial setup, but it’s also very rewarding !

Here are a few pointers I can give you:

• Using a good domain is important, some provider block entire TLDs for cheap domains (eg. .tk or .pw). I learnt it the hard way…
• Set your MX records to A records, not CNAME
• Ensure your PTR records match your A records for the mail server
• Learn about SPF and DKIM
• Set them up, and verify with mxtoolbox
• Use the ip4:<ipv4> and/or ip6:<ipv6> selectors for SPF
• Setup a spamfilter (I like spamassassin)
• Leave it all running for a few weeks/months
• Publish a DMARC policy on your DNS, and verify with mxtoolbox

This should limit a lot your likeliness to end up in spam folders (which is usually the hardest part about running your mail server)

ELI5

So it’s saturday afternoon, a very hot one, so you ask your daddy for an ice cream (hosted service). The shop you go in is very bizarre though, as there is one vendor (TCP port) for each flavor (docker service/virtualhost). But it’s tricky because they’re all roaming in the shop, and you don’t know who’s responsible for each flavor. Your dad is also not very comfortable paying these vendors directly because they only accept cash and do not provide any receipt (self-signed certificate/no TLS).

Hopefully, there is the manager (reverseproxy) ! This girl is right where you expect her: behind the counter (port 80/443), accept credit cards and has a receipt machine (Domain name + associated certificate). She also knows everyone on her team, and who’s responsible for each flavor !

So you and your dad come to see the nice lady, ask for a strawberry + chocolate ice cream, and pay her directly. Once done, she forwards your request directly to the vendors responsible for each flavor, and give you back your ice cream + receipt. Life is good, and tasty !