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Business email that lands in the inbox, not the spam folder

SPF, DKIM and DMARC explained without the acronym soup, why your mail goes to spam, and how to set up email on your own domain properly.

4 min read
Business email that lands in the inbox, not the spam folder. An article by Athabasca Solutions.

Email on your own domain is one of the cheapest credibility upgrades a small business can make, and one of the easiest to get subtly wrong. Wrong here does not mean broken. It means your quotes land in spam and you find out because a client mentions it in passing, months later.

The whole subject is three DNS records and one habit. Here they are without the acronym soup.

Why anything goes to spam at all

Email was designed with no way to prove who sent a message. Anyone can put your address in the From field, which is why phishing works.

Everything since has been layers bolted on so a receiving mail server can answer one question: did the organisation that owns this domain actually authorise this message? If the answer is unclear, the safe move is the spam folder, and receivers have become much less forgiving about unclear.

Three records provide the answer.

SPF, the list of who may send

An SPF record is a line in your DNS naming which servers are allowed to send mail for your domain. The receiver checks the connecting server against that list.

Two things go wrong with it constantly:

More than one SPF record. This is not additive, it is a failure. Adding a second record when you add a new mail service breaks the first one. Everything goes into one record.

Too many lookups. SPF permits ten DNS lookups and each include: for a third party service can consume several. Businesses using a mail host, a newsletter tool and a CRM quietly blow the limit, and the result is a permanent error that nothing announces.

DKIM, the signature

DKIM puts a cryptographic signature on every outgoing message, and publishes the matching public key in DNS. The receiver verifies that the message was signed by someone holding your key and was not altered in transit.

Your mail provider generates the key and gives you a long value to paste into DNS. The usual failure is truncation, because the value is long and some DNS interfaces split or trim it. A key that is one character short fails silently, so it is worth verifying the published record after adding it rather than trusting the paste.

DMARC, the instruction

DMARC ties the other two together and tells receivers what to do when a message fails: nothing, quarantine, or reject. It also asks receivers to send you reports about mail claiming to be from your domain.

Start at none. A DMARC policy of p=none changes nothing about delivery and starts the reports flowing. Read them for a month, find the legitimate systems you had forgotten were sending as you, fix those, and only then move to quarantine and eventually reject.

Going straight to reject is how a business discovers that its invoicing system sends from its domain, by having every invoice bounce.

The habits that matter more than the records

Never send bulk mail from your main domain without care. Newsletters and transactional mail should go through a service, ideally on a subdomain, so a bad campaign cannot damage the reputation of the domain your quotes go out from.

Do not buy lists. Nothing damages deliverability faster than complaints, and nothing generates complaints like mail people did not ask for.

Keep the domain warm and consistent. Reputation attaches to a domain and a sending server over time. Switching providers repeatedly resets that.

Publish an MX record even if you do not receive mail on a domain, or publish a null MX. Domains with no policy are attractive to spoof.

What it costs

Roughly one to five dollars per mailbox per month from a dedicated mail host, more from the large office suites. For a business of five people that is somewhere between five and fifty dollars a month depending on whether you need the documents and calendar suite or just mail.

There is a real decision here between a mail host and a full office suite, and it is mostly about whether you already live in one of those ecosystems. Mail alone is dramatically cheaper, and webmail from a dedicated host is perfectly usable, which means staff do not have to configure anything on their own devices.

Verifying it actually works

After setup, do not trust the vendor’s checkmark. Send a message to an address on a different provider and inspect the headers, which every mail client can show. You are looking for three passes: SPF, DKIM and DMARC alignment.

It is also worth checking DNS against more than one public resolver, because propagation and negative caching mean a tool can report failure for records that are correct and live. A record that resolves correctly from several independent resolvers is correct, whatever a dashboard says.

If your mail is going to spam and you would rather someone just fixed it, tell us your domain and who hosts your mail.

Related: what hosting actually costs, choosing a web developer in Alberta, and our cloud and hosting work.

Further reading

Sections covered in Business email that lands in the inbox, not the spam folder: Why anything goes to spam at all, SPF, the list of who may send, DKIM, the signature, DMARC, the instruction, The habits that matter more than the records, What it costs, Verifying it actually works
The shape of the argument, in order.

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