Why are my emails going to spam all of a sudden?

The usual triggers: a complaint rate that crossed Gmail's thresholds, authentication that broke during a DNS or ESP change, a jump in send volume, or months of mailing unengaged profiles finally catching up. Check Google Postmaster Tools first; its domain reputation graph usually shows when the slide started and how steep it is.

What spam complaint rate is acceptable?

Google enforces at 0.3% and recommends staying under 0.1%; Yahoo applies matching rules. Those are fleet-average numbers across your recent sends, so one bad campaign can push a small sender over. One-click unsubscribe is your pressure valve: an unsubscribe costs you a subscriber, a spam report costs reputation.

Does SPF, DKIM, and DMARC guarantee inbox placement?

No. Authentication is an entry requirement, not a ranking boost. Since February 2024, bulk senders to Gmail must have all three plus one-click unsubscribe just to be considered normally. Placement after that is earned with engagement: mail that gets opened and clicked inboxes, mail that gets ignored drifts to spam.

How do I actually measure inbox placement?

Seed testing. Services like GlockApps deliver your campaign to a panel of real Gmail, Outlook, and Yahoo addresses and report the folder it landed in. ESP dashboards cannot do this; their "delivered" metric counts spam-folder arrivals as success. We run a seed baseline in week one of every deliverability engagement.

Resources · Deliverability

Why emails go to spam: the 2026 checklist

By Theo Ramaker, Lifecycle Automation Lead · Published June 15, 2026 · Updated July 26, 2026

Emails go to spam for four reasons: broken authentication, high complaint rates, sustained sends to people who ignore you, and list-quality rot. Everything else is a variation. Since February 2024, when Gmail and Yahoo's bulk-sender rules took effect, the tolerances have been explicit numbers rather than folklore. This checklist walks the four causes in the order we check them on client domains.

Is your authentication actually aligned?

Bulk senders (5,000+ messages a day to Gmail) must publish SPF, DKIM, and DMARC, per Google's sender guidelines, and the details bite. DKIM signing with your ESP's shared domain instead of your own breaks DMARC alignment even though each record looks valid alone; that exact miss cost a fitness app client 22 points of inbox placement before we found it. Check all three records, then check alignment, not just existence.

What is your complaint rate, really?

Google enforces spam-complaint rates at 0.3% and recommends staying under 0.1%. Two mechanical fixes move this number fast. First, RFC 8058 one-click unsubscribe in your headers, required under the 2024 rules, gives tired subscribers an exit that does not damage you; an unsubscribe is a lost profile, a complaint is lost reputation. Second, stop mailing the people most likely to complain: profiles who have not engaged in months.

Are you sending to people who stopped reading?

Mailbox providers grade you on how recipients treat your mail. Sends to silent profiles accumulate as evidence against you, which is why suppression is the strongest single move in most repairs. The fitness app in our deliverability write-up suppressed 29% of a 78k list; complaints fell from 0.36% to 0.05%, and Gmail placement climbed from 78% to 98% in seven weeks. The scoring model behind suppression decisions is in the segmentation strategy guide.

How do you measure placement you cannot see?

Your ESP's "delivered" number counts spam-folder arrivals as delivered; it cannot tell you where mail landed. Two tools close the gap:

GlockApps seed tests: your campaign goes to a panel of real Gmail, Outlook, and Yahoo inboxes and you get folder-level placement per provider.
Google Postmaster Tools: Gmail's own view of your domain reputation, spam rate, and authentication results over time. Free, and the first thing we open in any diagnosis.

The checklist, in order

Verify SPF, DKIM, and DMARC exist and align on your sending domain.
Confirm RFC 8058 one-click unsubscribe headers are live.
Pull complaint rate; alarm at 0.1%, emergency at 0.3%.
Run a GlockApps seed baseline across Gmail, Outlook, Yahoo.
Open Google Postmaster Tools and read the reputation trend.
Suppress profiles silent past your engagement threshold.
Restrict sends to engaged segments; widen as reputation recovers.
Keep monthly seeds and complaint alerts running permanently.

Steps six and seven are where most self-service repairs stall, because they require the segmentation infrastructure to exist. If that is the missing piece, our Deliverability Repair service runs the whole sequence, monitoring included.