Why your emails land in spam and what fixes it

You wrote a good email, sent it to two thousand people, and almost nobody opened it. The temptation is to blame the subject line. Usually the subject line was fine. The email simply never reached the inbox.

Deliverability is the least glamorous part of marketing and the one that quietly decides whether any of the rest works. Here is what actually controls it, in the order it matters.

Inbox providers are grading you, constantly

Gmail, Outlook and Yahoo are not reading your email and judging the writing. They are watching behaviour and building a reputation score for the domain you send from.

They watch how many people open and reply, how many delete without reading, how many mark you as spam, how many addresses bounce, and whether your sending volume looks steady or erratic. Good signals earn you the inbox. Bad ones earn you the spam folder, and the fall is much faster than the climb back.

Two things follow from that. Reputation belongs to your domain, so it travels with you. And it is earned slowly, which means shortcuts do not exist.

Send from your own domain, properly authenticated

If you send marketing email from a free address, you are borrowing somebody else's reputation and inheriting their problems. Send from your own domain instead, and set up the three authentication records that prove the mail is really from you.

In plain terms, SPF says which servers are allowed to send for your domain. DKIM adds a signature that proves the message was not altered. DMARC tells providers what to do when something fails those checks, and it is the one most businesses skip.

You do not need to understand the cryptography. You need these records in place before you send anything at volume, because the major providers now treat them as a baseline rather than a bonus.

Warm up before you scale up

A brand new domain sending two thousand emails on day one looks exactly like a spammer, because that is what spammers do.

Warming up means starting small and increasing gradually over a few weeks. Begin with your most engaged people, the ones who will actually open and reply, and grow the volume steadily. You are teaching the providers that mail from your domain is wanted.

The same applies after a long silence. If you have not emailed your list in eight months, do not restart with a blast to everybody. Restart with the people who engaged most recently and build back up.

Your list is the biggest lever, not your copy

Most deliverability problems are list problems wearing a copy costume.

Only email people who asked. Bought lists, scraped addresses and "they are in my industry so they will find it useful" are how good domains get ruined. One sending reputation, thousands of strangers, no way back.

Clean out the dead weight. Addresses that no longer exist cause hard bounces, and hard bounces hurt. If somebody has not opened anything in six months, either run one honest re engagement message or stop sending to them.

Watch the complaint rate obsessively. People marking you as spam is the single fastest way to lose the inbox. If a campaign spikes complaints, stop, look at who you sent it to, and fix the targeting before you send again.

Make unsubscribing easy. Hiding the link does not keep subscribers, it converts them into complainers, which is far more damaging. A visible unsubscribe is protection, not leakage.

Understand bounces before you panic

A hard bounce means the address does not exist or the server permanently refused you. Remove those immediately and never send to them again.

A soft bounce is temporary. A full mailbox, a server having a bad day, a message that was too large. Those can be retried, and a few of them are normal.

The mistake is treating all bounces the same and either ignoring them or purging aggressively. Separate the two, act on the hard ones, monitor the soft ones for patterns.

Write mail that earns engagement

Once the technical side is right, the content does the rest of the work, because engagement is what sustains reputation.

Send to people who want it, at a rhythm they expect. One useful email a fortnight beats four rushed ones a week. Ask questions that invite replies, because a reply is the strongest positive signal there is. Keep image heavy templates for the occasions that need them, since plain text style mail from a real person usually performs better and looks less like a broadcast.

And segment. A message written for everybody gets ignored by everybody. The same effort split across two smaller, better targeted sends will beat one big generic one on every metric that matters.

A simple health routine

Check these monthly and you will catch problems while they are small.

• Open rate and click rate by segment, not just overall
• Bounce rate, separated into hard and soft
• Complaint rate, watched per campaign
• Unsubscribe rate, which is a signal about relevance rather than a failure
• Whether your volume is steady or spiky

If open rates drop across the board while your content stayed the same, that is not a copy problem. That is a placement problem, and you should stop sending and investigate before you dig the hole deeper.

What good looks like

Your mail lands in the main inbox. Your open rates hold steady instead of drifting down every quarter. When you launch something, the people who already trust you actually see it, which means the launch works without buying more traffic.

That is the real return on this unglamorous work. You already paid to build the list. Deliverability decides whether you get to use it.

What to do next

Pick one thing today. Check whether SPF, DKIM and DMARC are set up on the domain you send from. If you cannot answer that quickly, that is your starting point, and it is usually a thirty minute job with a much bigger payoff than another rewrite of your subject line.

If you would rather have the whole sending setup audited, the records, the warm up plan and the list hygiene, bring me your current numbers and we will work out what is costing you the inbox.