Why Your Emails Land in Spam — and How SPF, DKIM & DMARC Fix It

If your business emails keep landing in customers' spam folders, three little-known settings are usually the cause — and the fix. Here is what SPF, DKIM, and DMARC do.

You send an important quote to a customer, and it never gets a reply — because it quietly landed in their spam folder. For businesses, poor email deliverability costs real money in lost deals and missed communication. The most common cause is missing email authentication. This guide explains the three records that fix it, in language that does not require a technical background.

Why legitimate emails get marked as spam

Email providers like Gmail and Outlook are constantly fighting spam and fraud. To decide whether to trust your email, they check whether it is genuinely authorised to come from your domain. If you have not set up the records that prove this, your perfectly legitimate emails can look suspicious — and get filtered into spam, or rejected entirely.

The three records that build trust

SPF — who is allowed to send for you

SPF (Sender Policy Framework) is a published list of the mail servers permitted to send email on behalf of your domain. When an email arrives, the receiving server checks whether it came from one of your approved senders. If it did, that is a point in favour of delivery; if it did not, the email looks like a forgery.

DKIM — a tamper-proof signature

DKIM (DomainKeys Identified Mail) adds an invisible digital signature to every email you send. The receiving server uses this signature to confirm two things: that the email genuinely came from your domain, and that it was not altered in transit. It is the email equivalent of a sealed, signed envelope.

DMARC — your policy and your eyes

DMARC (Domain-based Message Authentication) ties SPF and DKIM together and tells receiving servers what to do if an email fails the checks — for example, send it to spam or reject it outright. It can also send you reports showing who is trying to send email using your domain, which helps you spot impersonation attempts.

How to know if yours are set up

If your business emails frequently land in spam, or contacts say they never received messages you sent, there is a good chance one or more of these records is missing or misconfigured. They are published as DNS records on your domain, and they need to be configured correctly for your specific email provider.

How to fix it

1. 1Identify the mail service you use to send business email.
2. 2Add the correct SPF record listing your authorised senders.
3. 3Enable DKIM signing through your email provider and publish the matching record.
4. 4Add a DMARC record, starting with a monitoring policy, then tightening it once everything passes.
5. 5Test your setup and check that emails to Gmail, Outlook, and others arrive in the inbox.

This is fiddly to get exactly right, and small mistakes can stop email working altogether — so it is one area where it pays to have it set up properly the first time. A provider that manages your domain, hosting, and email together can configure all three records correctly as part of your setup.

The takeaway

Email that lands in spam is a silent business killer. SPF, DKIM, and DMARC are the standard, expected way to prove your emails are genuine — protecting both your deliverability and your reputation. If you are not sure yours are configured, it is well worth checking before your next important message disappears.

Written by the Saby Infotech team

Saby Infotech is a software development company based in Dar es Salaam, Tanzania. Over 10+ years we've delivered 50+ websites, hosting setups, and custom systems for 30+ businesses across 9+ industries — from safari operators and schools to NGOs and energy companies. These guides come from real project experience helping Tanzanian businesses get online and grow.

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