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/orip6:<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)
I get what you say, and you’re definitely not wrong to do it. But as I see it, you only saved ~80Kib of ingress and a few lines of logs in the end. From my monitoring I get ~5000 failed auth per day, which account for less than 1Mbps average bandwidth for the day.
It’s not like it’s consuming my 1Gbps bandwidth or threatening me as I enforce ssh key login. I like to keep things simple, and ssh on port 22 over internet makes it easy to access my boxes from anywhere.