Why are my emails suddenly going to spam?

A sudden change usually means a broken or changed authentication record (SPF/DKIM/DMARC), a reputation hit from a volume spike or complaints, or sending to an unengaged/old list. Check authentication first, then reputation and list hygiene.

Does SPF, DKIM and DMARC guarantee inbox placement?

No — they are necessary but not sufficient. They let providers trust you are who you say; placement then depends on sender reputation, engagement and content. But failing authentication almost guarantees spam for bulk senders.

What complaint rate is too high?

Keep spam complaints under about 0.1%. Gmail flags senders above roughly 0.3%, after which filtering becomes aggressive and hard to recover from.

Why your emails go to spam (and how to fix it)

By VigilDog Team · August 11, 2026 · 7 min read

When legitimate email lands in spam, it is almost never one thing — it is a score. Inbox providers weigh authentication, sender reputation, content and recipient engagement, and if enough signals look wrong, they filter you out. Here is what actually moves that score, in priority order.

First: authentication (the table stakes)

If your SPF, DKIM and DMARC are not aligned, providers cannot verify the mail is really from you — and since 2024, Gmail and Yahoo require authentication for bulk senders outright. This is the first thing to fix because nothing else matters if you fail it.

Confirm all three are correct with the free SPF & DMARC checker, and if any need work, follow how to fix SPF, DKIM and DMARC.

How SPF, DKIM and DMARC verify an email

Sender reputation

Providers track the reputation of your sending domain and IP over time. New domains have no reputation (so they are treated cautiously), and a spike in volume or complaints tanks it fast. If you recently started sending, warm up gradually rather than blasting your whole list on day one.

Check whether your domain or IP is on a major blocklist, and keep your complaint rate under ~0.1% — above ~0.3% and Gmail will start filtering aggressively.

List hygiene and engagement

Inbox placement is increasingly driven by engagement: opens, replies, and the absence of "mark as spam". Sending to old, unengaged, or purchased lists is the fastest way to spam — hard bounces and spam-traps signal that you do not maintain your list.

Remove hard bounces immediately and suppress addresses that have not engaged in 6–12 months.
Never buy or scrape lists — they are full of spam traps that blocklist you.
Make unsubscribing one click (also a 2024 Gmail/Yahoo requirement) — it is far better than a spam complaint.
Ask new subscribers to reply or whitelist you; early engagement builds reputation.

Content and formatting

Content matters less than authentication and reputation, but obvious triggers still hurt: spammy subject lines (ALL CAPS, "FREE!!!", excessive emojis), a single giant image with no text, link shorteners, mismatched or unfamiliar from-domains, and missing a plain-text version.

Send from a consistent, authenticated from-address on your own domain — not a no-reply on a shared ESP domain — so your identity is stable and recognizable.

Keep it fixed

Deliverability degrades quietly: a DNS edit breaks DKIM, a new tool starts sending unaligned, or a DMARC record gets changed. You will not get an error — your open rates just drop. VigilDog's email monitoring watches your SPF, DKIM and DMARC so a change is a heads-up, not a mystery you discover weeks later.

Frequently asked

Why are my emails suddenly going to spam?: A sudden change usually means a broken or changed authentication record (SPF/DKIM/DMARC), a reputation hit from a volume spike or complaints, or sending to an unengaged/old list. Check authentication first, then reputation and list hygiene.
Does SPF, DKIM and DMARC guarantee inbox placement?: No — they are necessary but not sufficient. They let providers trust you are who you say; placement then depends on sender reputation, engagement and content. But failing authentication almost guarantees spam for bulk senders.
What complaint rate is too high?: Keep spam complaints under about 0.1%. Gmail flags senders above roughly 0.3%, after which filtering becomes aggressive and hard to recover from.

Keep reading

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