How to stop emails going to spam (and find out why they are)

Your emails are going to spam, and nobody sent you a notice. Replies dried up, a teammate's test landed in Junk, or a prospect mentioned they found you there. The good news: the causes are a short list, and you can check most of them in an afternoon. Here's how to stop emails going to spam, starting with finding out why.

First, confirm it (and find where)

"Going to spam" is often a guess. Before you change anything, find out where your mail actually lands and with which providers.

• Send a test to real inboxes at Gmail and Outlook, from the same inbox and with the same copy as the campaign. Gmail and Microsoft often disagree.

• Read the headers. In the received message, look for spf=pass, dkim=pass and dmarc=pass. Anything else is your first fix.

• Check Google Postmaster Tools for your sending domain. It shows Gmail's view of your domain's reputation and your spam complaint rate.

• Read your bounces. Spam blocks often come back as bounces with a reason attached. Our bounce code library explains each code and whose problem it is.

Why are my emails going to spam?

Almost every case comes down to one or more of these five.

1. Authentication is missing or broken

SPF, DKIM and DMARC tell the receiving server that the message really came from your domain. Gmail and Yahoo require all three from bulk senders, and they reject or filter mail that fails. A bounce like 550 5.7.26 is Gmail saying exactly this.

2. The domain has no reputation yet, or lost it

A brand-new domain has no history, and mailbox providers are wary of any domain that suddenly sends a lot. Volume that jumps from zero to full in a week looks like a spammer, whatever the copy says. Older domains lose reputation the same way: a spike, a bad list, a wave of complaints.

3. People mark you as spam

Complaints are the strongest signal there is. Google's sender guidelines say to keep the spam rate shown in Postmaster Tools below 0.1% and never let it reach 0.3%. You can't control every click, but you can control who gets the email: tight targeting and relevant copy are deliverability work.

4. The list is bad

Sending to addresses that don't exist tells providers you don't know who you're emailing. A bad list shows up as bounces first and spam placement soon after. High email bounce rate? Burned domain or bad list shows how to tell the two apart.

5. The content looks like spam

Link shorteners, lots of links, image-only emails, attachments in a first touch and a tracking domain shared with thousands of other senders all add risk. Each on its own rarely sinks you; stacked together they do.

How to stop emails going to spam

Work through these in order. The early ones fix the most.

1. Authenticate every sending domain. Publish SPF and DKIM for every service that sends as you, and a DMARC record. Start DMARC at p=none and tighten it once you're sure every sender passes.

2. Send cold email from separate domains. Keep outreach off the domain your team uses for customers and invoices, so a bad week in outbound can't touch the mail that matters most.

3. Warm up, then ramp slowly. New domains and inboxes need a sending history before they carry campaigns. In SendingOS, warmup runs on a pool of real Google and Microsoft inboxes only, with no SMTP accounts in it.

4. Clean the list before the first send. Verify addresses and drop anything that bounces. In SendingOS, email verification is free, so there's no reason to skip it.

5. Write like a person. Plain text, one link at most, no attachments, a reason this person is getting this email. If you track clicks, use a tracking domain that's yours.

6. Make leaving easy. An easy way to opt out costs you one contact; a spam complaint costs you the domain.

7. Watch the signals every day, and act early. A domain rarely burns overnight; it drifts. In SendingOS, domain health rules spot a drifting domain and pause its inboxes on their own, before the whole campaign suffers.

For agencies: keep clients apart

If you run outbound for several clients, one client's bad list can drag down everyone sharing the same sending infrastructure. In SendingOS, every client workspace sends on its own isolated IPs, so one client's bad list can't drag down another client's IP reputation.

When it's already too late

If a domain is already burning, more fixes to copy won't save this week's sends. Pause it, keep warmup running, fix what burned it, and bring it back slowly. High email bounce rate? Burned domain or bad list covers the recovery in more detail.