Why are my marketing emails going to spam?

The usual causes, in order of how often they turn out to be the culprit: missing or misaligned authentication (SPF, DKIM, DMARC), a spam complaint rate above the mailbox providers' threshold, sending to unengaged or purchased contacts, and a sending domain with no history. Fix authentication first — it is the fastest win and unauthenticated bulk mail is now rejected or filtered by default.

What are the Gmail and Yahoo bulk sender requirements?

If you send roughly 5,000 or more messages a day to Gmail addresses, you must authenticate with SPF and DKIM, publish a DMARC record with aligned authentication, offer one-click unsubscribe in the message headers (RFC 8058), and keep your spam complaint rate low — under 0.10% in practice, and never at or above 0.30%. Yahoo and Microsoft apply closely matching rules.

How long does warming a new sending domain take?

Plan for four to six weeks. Start with your most recently engaged subscribers at low volume, then increase gradually while watching bounce and complaint rates. Volume is only half of it — who you send to matters more. Warming on your most engaged contacts builds reputation; warming on a cold list destroys it faster than not warming at all.

What spam complaint rate is safe?

Keep it below 0.10%, which is one complaint per thousand delivered messages. Google publishes 0.30% as the level where enforcement kicks in, but treating that as your target leaves no margin — by the time you can see 0.30% in Postmaster Tools, filtering has usually already started.

Should I use a dedicated IP or a shared IP?

Shared IPs are the right default for most stores. A dedicated IP only builds reputation if you send consistently high volume; below that, your sending is too sparse to establish a track record, and you get the risk of an unwarmed IP with none of the benefit. Domain reputation matters more than IP reputation for most senders anyway.

Email Deliverability: How to Land in the Inbox, Not Spam

Deliverability is the one part of email marketing where doing nothing has a cost. Your best-written campaign converts nothing from the spam folder, and by the time you notice — revenue quietly down, opens quietly down — you have usually been filtered for weeks.

This guide covers the technical setup that gets you trusted, the rules Gmail and Yahoo now enforce on bulk senders, how to warm a new sending domain, and a diagnostic sequence for when your mail is already landing in spam.

What deliverability actually measures

Two terms get used interchangeably and should not be.

Delivery rate — the share of messages a mailbox provider accepted rather than bounced. Easy to measure. Nearly always looks fine.
Deliverability — the share that reached the primary inbox rather than spam or a promotions bucket. Harder to measure and the number that determines your revenue.

A 99% delivery rate is perfectly compatible with half your mail sitting in spam. Mailbox providers accept and then quietly file. That gap is why a sudden drop in clicks with no change in bounces is nearly always a deliverability problem, not a copy problem.

Authentication: the part that is not optional

Authentication proves that mail claiming to come from your domain actually did. Without it, bulk mail is filtered or rejected outright.

SPF

A DNS TXT record listing which servers may send for your domain. Two things to watch: you may only publish one SPF record per domain (multiple records is a hard failure, and it happens constantly when a second tool is added), and SPF has a limit of ten DNS lookups — chained includes silently blow past it.

DKIM

A cryptographic signature added to every outbound message, with the public key published in DNS. Your sending provider generates the key pair and tells you which records to publish. Use a selector per provider so you can add or remove a sender without breaking the others.

DMARC

The policy layer. DMARC tells mailbox providers what to do when SPF or DKIM fails, and where to send aggregate reports. Publish it in three stages:

p=none — monitor only. Collect reports for two to four weeks and find every legitimate sender you had forgotten about (the invoicing tool, the helpdesk, the CRM).
p=quarantine — failing mail goes to spam. Roll out with a percentage tag first if your volume is meaningful.
p=reject — failing mail is refused. The end state, and the one that actually protects your domain from spoofing.

The detail people miss is alignment. DMARC does not just require SPF or DKIM to pass; it requires the passing domain to match the domain in your visible From address. Mail can pass SPF for your provider's domain and still fail DMARC. Check alignment, not just pass/fail.

BIMI

Optional, and only eligible once DMARC is at quarantine or reject. It displays your logo next to your messages in supporting clients, which helps recognition. Treat it as a finishing touch, not a fix.

The bulk sender rules you have to meet

Google, Yahoo, and Microsoft have converged on a shared baseline for high-volume senders — roughly 5,000 or more messages a day to a given provider's users. The requirements:

SPF and DKIM on every message, with at least one aligned to your From domain.
A published DMARC record on the sending domain. p=none satisfies the letter of it; enforcement is better.
One-click unsubscribe in the message headers (RFC 8058, the List-Unsubscribe-Post header), honoured within a couple of days. A visible unsubscribe link in the body is still required — this is in addition to it.
Valid forward and reverse DNS on the sending IP, and TLS on the connection.
A spam complaint rate that stays low. Google publishes 0.30% as the enforcement threshold and recommends staying under 0.10%.

Treat 0.10% as the ceiling, not the target. Complaint rate is a lagging indicator: the filtering starts before the number in your dashboard catches up.

If you send through CampGain, the provider you connect — SendGrid, Resend, or Gmail SMTP — handles the transport-level items. The DNS records and the list quality are yours.

Reputation: domain first, IP second

Sender reputation is built from how recipients treat your mail, and it attaches to two things.

Domain reputation follows your sending domain everywhere. It is the one that matters most for typical ecommerce volume, and it does not reset when you switch providers.
IP reputation attaches to the sending IP. On a shared pool you inherit the pool's behaviour; on a dedicated IP you build your own from zero.

Which means the dedicated-IP question has a clearer answer than it usually gets: a dedicated IP only pays off if you send enough, consistently enough, to establish a pattern. Below that, sparse sending from a dedicated IP looks like a dormant sender waking up every few weeks — which is exactly what spam looks like. Most stores should stay on a shared pool and put the effort into domain reputation and list quality.

The signals that move it

Complaints — the heaviest negative signal by a wide margin.
Hard bounces — invalid addresses suggest a list you did not build yourself. Keep under about 2%, and suppress permanently on the first hard bounce.
Spam trap hits — recycled or pristine addresses that exist only to catch bad list practice. Zero tolerance; a hit means your acquisition or hygiene is broken.
Positive engagement — opens, clicks, replies, and being moved out of spam all count in your favour. This is why sending only to engaged contacts during a repair actually works.

Warming a new sending domain

A new domain has no history, and mailbox providers treat "no history plus sudden volume" as the classic spam signature. Ramp deliberately:

Weeks 1–2 — send only to contacts who engaged in the last 30 days, at low daily volume. These people open, and those opens are the reputation you are buying.
Weeks 3–4 — expand to 60- then 90-day engaged contacts, increasing volume gradually. Watch bounce and complaint rates after every step and hold if either moves.
Weeks 5–6 — reach full volume, keeping unengaged contacts out until the ramp is complete.

The mistake is treating warming as a volume schedule alone. Who you send to during the ramp matters more than how many. Warming on a cold list builds a bad reputation faster than not warming at all.

List hygiene is a deliverability control

Most "our deliverability collapsed" stories are list stories.

Suppress hard bounces immediately and never re-add them, even if they come back through a form.
Set a sunset policy. Contacts with no opens, clicks, or orders in six to twelve months should stop receiving regular sends. Give them one re-permission campaign, then let them go.
Use double opt-in where acquisition is noisy — paid lead magnets, giveaways, offline capture. It costs you subscribers and saves you a sending programme.
Never buy, rent, or scrape a list. Purchased lists are how you hit spam traps, and no amount of technical setup survives that.

The counterintuitive part: cutting your list often increases total revenue, because the mail that remains reaches people who wanted it. Our customer segmentation guide covers how to build engagement tiers you can actually send against.

Content signals that still matter

Content is a smaller factor than authentication and reputation, but it is not zero:

Keep a real text-to-image balance. An email that is one giant image gives filters nothing to read and breaks entirely when images are blocked.
Send a plain-text alternative alongside the HTML. Its absence is a small negative signal and it costs nothing.
Keep your From name and address consistent. Recognition drives engagement, and engagement drives placement.
Watch link reputation. Link shorteners and domains you do not control are a genuine risk — a shortener that other people abuse drags your mail down with it.
Write like a person. Chasing a "spam word list" is mostly folklore, but all-caps subject lines, walls of exclamation marks, and hidden text are real patterns filters recognise.

Diagnosing a live problem

If your mail is already going to spam, work in this order rather than changing five things at once.

Verify authentication end to end. Send to an address you control at each major provider and inspect the headers for SPF, DKIM, and DMARC results — including alignment.
Check Google Postmaster Tools. It shows your domain reputation and spam rate for Gmail. A complaint rate spike will usually name the date the trouble started.
Line the date up against what you changed. New sending domain, new template, a big import, a list you had not mailed in a year — the cause is normally in that list.
Segment by provider. If Gmail is fine and Outlook is not, it is a provider-specific reputation issue, not a broken record.
Shrink to your engaged core. Send only to contacts who engaged in the last 30 days for two to three weeks. Rebuilding positive signal is slower than losing it, and there is no shortcut.
Fix acquisition before you scale back up. If the source of the bad contacts is still running, you will be back here in a quarter.

Where CampGain helps

CampGain does not replace your DNS setup — no platform can — but it removes the guesswork from what happened after you pressed send.

Per-contact delivery detail. Every campaign shows sent, delivered, opened, and clicked per step and per recipient, with the provider's stated reason on anything that failed. A bounce that says why is a bounce you can act on.
Test sends before launch. Send the full workflow to a handful of addresses, check rendering and headers, and only then release it to the segment.
Segments that support a sunset policy. Combine your own engagement conditions with Shopify data to build the engaged-only audiences a warm-up or a repair depends on.
Your own sending provider. You connect SendGrid, Resend, or Gmail SMTP, so the reputation you build stays yours.

See what the platform includes for the full picture.

The short version

Publish SPF, DKIM, and DMARC and confirm alignment. Meet the bulk sender baseline before you need to. Warm new domains on engaged contacts only. Suppress bounces, sunset the dormant, and never buy a list. Then watch complaint rate as closely as you watch revenue — it is the metric that predicts whether the rest of your email programme gets to work at all.

With that foundation in place, the campaigns in our ecommerce email marketing guide can actually reach the people you built them for.