Why your emails go to spam, and how to fix it

Deliverability comes down to three things: can you prove the mail is yours, does your domain have a decent reputation, and does the message look like spam.

1. Prove the mail is yours

Three DNS records do this. Missing any of them costs you.

SPF

Lists which servers may send email as your domain.

v=spf1 include:spf.protection.outlook.com -all

Two rules people break constantly:

• One SPF record only. Two is treated as a permanent failure, not

as "try both". If you use several senders, merge them into one record with multiple include: terms.

• Ten DNS lookups maximum. Each include: costs one. Go over and

the whole record fails.

End with -all (hard fail) once you're confident every legitimate sender is listed. Use ~all (soft fail) while you're still checking.

DKIM

Signs your outgoing mail cryptographically, so a receiver can verify it wasn't altered and really came from you. Your mail provider gives you the record to publish. In Microsoft 365 it's under Security → Email authentication, and you have to explicitly enable it after publishing — a step that's easy to miss.

DMARC

Tells receivers what to do when SPF and DKIM fail, and asks them to report back.

v=DMARC1; p=none; rua=mailto:dmarc@yourdomain.com

Start at p=none. Read the reports for two weeks — they'll show you senders you'd forgotten about, like a CRM or an invoicing tool. Once everything legitimate passes, move to p=quarantine, then p=reject.

Going straight to reject is how people accidentally block their own accounting software.

2. Reputation

• Never buy a list. One purchased list can poison a domain's

reputation for months.

• Honour unsubscribes immediately. Someone who can't get off your

list marks you as spam instead, and complaints hurt far more than an unsubscribe.

• Remove hard bounces. Repeatedly mailing dead addresses is a strong

spam signal.

• Warm up gradually. Sending 10,000 messages from a domain that

normally sends 50 a day looks exactly like a compromised account.

3. The message itself

• A subject line in ALL CAPS with exclamation marks
• One large image and almost no text
• Link shorteners
• "Click here" as your only call to action
• A from-address on a domain that doesn't match the links inside

None of these is fatal alone. Together they're a filter's checklist.

Testing it

Mail Tester gives you a score out of ten and tells you exactly what's missing. Send it a real message, not a test one — it grades the content too.

For a full audit of your domain's records, open a ticket. We'll check SPF, DKIM, DMARC and your reverse DNS, and tell you what to change.