Mail Reputation Management

There is a reason many like to use ESPs - Email Service Providers. Just setting up a good mail server is an arduous task, and generally pretty thankless. And at the end of that long, headache-filled road, your job is only beginning. It is one thing to be able to receive mail with minimal spammy fuss, it is quite another to be able to send it. Especially if you are a large community and your membership has you sending several thousand mails per day - or more.

The following is a basic checklist to help your mailserver maintain a positive reputation.

Check Blacklists

IP addresses have been moving around long before IANA handed out their final five /8 blocks. Often you will end up on one block or another that was once part of a smaller ISP whose address range was listed as dynamic, or a similar situation.

So don't be surprised if you're on a blocklist the moment you've got your IP. It happens - go through the removal process and get it taken care of.

Return Path Senderscore

If the list of ISPs and Freemail providers isn't a hint, the fact that Return Path also handles Hotmail and Yahoo as well makes this company's opinion of you disproportionately important. Keep an eye on your sender score, and take action if it gets too low - less than 90 is bad news, and you are in for hurt if you go below 70.

Note that Senderscore matters rather less if you send a lot of mail. "A lot" depends on the recipient - about 60% of my mail goes to Google, and they are a lot more aware of what my users are expecting than say, AoL is (sitting at ~1%), who is a lot more aware than j random isp who I might send a dozen mails a month to.

Whitelist Signup

• DNS Whitelist – Protect against false positives - This is the major one. At least one blacklist automatically checks this to make sure you're not on it.
• Junkemailfilter's list - Not as commonly referenced, but also the only other free whitelist I know of.

Sign up for feedback loops

The big ones:

• Hotmail's Junk Mail Reporting Program - Requires a certain degree of verification typically.
• Yahoo Complaint Feedback Loop - as annoying as Yahoo is, I find the fact that they use DKIM and track by mailing domain makes dealing with these much easier.
  • If you send Yahoo a lot of mail, you can try to get on Yahoo's bulk sender list, but this is not an easy or guaranteed process. This takes quite a bit of proactive work on the part of the one asking for it. Make sure your practices are clean, first and foremost.
• AOL Postmaster - Feedback Loop - Not many AoL addresses in my line of websites, but your mileage may vary. There are still a lot of people using them.
• Mail.ru - I don't send these people much mail personally, but you may find it necessary.

Return Path feedback loops (mostly ISPs and some smaller freemail providers). You can get a presumably up-to-date list here.

• Bluetie
• Comcast
• Cox
• Fastmail
• Tucows
• Rackspace/Mailtrust
• Time Warner
• Synacor
• Terra - In Portuguese, but standard Return Path form anyway.
• USA.net

• If someone from Return Path actually ever reads this, have you ever considered an automated Return Path signup system?

Other feedback loops:

• United Online (Juno/NetZero) - Trusted List - I get more mail from these people asking me to verify that I'm watching my abuse address then I ever get actual abuse reports from them.
• Zoho - Have maybe a dozen members who use them all told.
• Earthlink - You need to send them an email.

Debian Buster

Initial: Designing a Server - IPMI Installation - Second Steps

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Core: Network - OpenSSH - Packages - sysctl.conf - Iptables - Security - User Management

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Stack: Unbound - MariaDB - Nginx - PHP (7)

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Mail

Mail Setup - Mail Tables - OpenDKIM - Mail and DNS - Spamassassin - ClamAV - Postfix - Dovecot - Reputation Management

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Logs and Security: RKHunter - Logging - Logcheck - Backups - AppArmor