Selfhosted @lemmy.world vsis @feddit.cl 11mo ago

Receive only email server

Hello. Let's say I want to selfhost an email server (smtp + imap) that only will be used to receive email.

I only will send email internally (from my domain to my domain) and receive from 3rd parties.

Should I setup DKIM, DMARC, SPF and reverse IP lookup?

To be honest, I'm having a bit of hard time understanding the madness of email authentication. So I can't figure it out by myself if those mechanisms are needed in my case.

I haven't deployed anything, but probably will use Stalwart. It looks like it's easy to deploy. Is there any other beginner-friendly email service I should read about?

Thanks!

11 comments

You should definitely set up a DMARC record to prevent other people from using your email domain to send spam. If you don't have DMARC configured, other email servers will give any senders the benefit of the doubt and accept mail that claims to be from your domain.

You can just set the DMARC record to reject 100% of unverified mail and call it a day. Since you aren't sending anything it won't affect you.
- I would also set up SPF to disallow all IPs to send mail for that domain in case some system supports SPF but not DMARC.
  
  Thanks to both of you.
  
  I had the hope that DMARC, SPF and DKIM was stuff I could just ignore if not sending email. It seems I was wrong about that.
- Just to flesh that out a bit... All you need is to add a TXT record to your DNS records:
  
  Name: _dmarc.yourdomain.com
  
  Value: v=DMARC1; p=reject; pct=100
- will give any senders the benefit of the doubt and accept mail that claims to be from your domain.
  
  You misspelled "black-hole your domain forever".
- Some strict mail servers even blacklist you if the DMARC record is missing.
  
  Some servers blacklist you even if you have DMARC, SPF, DKIM, DNS setup perfectly, but your IP is in a block of addresses that may or may not have been hosted by the same ISP of some unrelated server that was possibly compromised 10 years before you even set up the mail server. Ask me how I know.
Should I setup DKIM, DMARC, SPF and reverse IP lookup?

This is no brainer to setup using mailcow. Just need to copy paste the provided TXT values from mailcow ui into your dns entries.

Mailcow is fantastic and very easy to deploy. I highly recommend it.
If your domain will NEVER send e-mail out, you only really need and SPF record to tell other servers to drop e-mail FROM your domain. Even that’s somewhat optional. If you ever plan on sending ANY outbound (you should at very least for the occasional ticket) then do DKIM, DMARC and SPF. The more of these you do, the less likely e-mails FROM your domain are to be flagged as spam.

11 comments