Cold Email Spam Checker: What Actually Gets Flagged in 2026

A bad spam checker counts scary words and gives you a score.

A good spam checker asks a harder question: what would make recipients and mailbox providers distrust this message?

That difference matters because modern cold email risk is not only lexical. It is behavioral, technical, and structural. A message can contain no obvious spam phrase and still create risk if it looks like a mass-generated template, hides the sender's identity, skips opt-out expectations, or pushes volume into an audience likely to complain.

Use the AI Cold Email Deliverability Checker if you want the full Folderly-style report. This guide explains what the checker is looking for and why.

The old spam-score model is too narrow

Legacy spam tools often focus on:

• trigger words
• exclamation points
• excessive capitalization
• link count
• HTML weight
• missing text version

Those checks still have value. They are not enough.

In 2026, the better review model includes five layers:

What gets flagged: copy that asks for trust too early

Cold email copy gets risky when it asks the recipient to believe too much before it proves relevance.

Risky:

Safer:

The first line is a claim. The second is a reason.

What gets flagged: subject lines with false familiarity

Subject lines do not need to trick people into opening. They need to set accurate context.

Risky subject patterns:

• "Re: quick question" when there was no prior thread
• "Following up" as a first message
• "Important account update" for a sales pitch
• "Final notice" for a non-urgent offer
• "You have been selected" for a broad prospecting campaign

Safer subject patterns:

• "Gmail-heavy outbound risk"
• "Question on SDR ramp"
• "One copy check before send?"
• "Reducing complaint rate"

The safer subjects are not boring. They are honest. That matters because Google explicitly warns against misleading sender behavior, and the FTC treats misleading subject lines as a core compliance issue for commercial email.

What gets flagged: missing unsubscribe logic

A cold email can be relevant and still need a clear opt-out path. Google says marketing and subscribed messages must support one-click unsubscribe and include a visible unsubscribe link in the message body for bulk senders. The FTC says commercial emails need a way for recipients to opt out, and opt-out requests must be honored within 10 business days.

For cold outbound, the practical rule is simple:

• include a clear unsubscribe or preference sentence in the body
• ensure your sending system can honor opt-outs fast
• do not make the recipient explain why they want out
• do not keep emailing someone who opts out, bounces, or replies negatively

An unsubscribe line will not make bad email good. It can reduce the chance that an annoyed recipient uses the spam button as the only visible escape.

What gets flagged: links before trust

Links are not automatically bad. But links before context create friction.

Common risky pattern:

1. link to website
2. link to calendar
3. link to case study
4. link to unsubscribe

For a first cold email, that is usually too much. It gives the recipient four decisions and gives filters more surface area to inspect.

Safer first email:

• zero or one contextual link
• one CTA, usually reply-based
• one clear opt-out path

If the recipient wants proof, send the proof in the next message or after a reply.

What gets flagged: sender setup uncertainty

Gmail's sender guidance says all senders need SPF or DKIM, while bulk senders need SPF, DKIM, and DMARC. It also says the From domain should align with either the SPF or DKIM domain for direct email.

That means a content checker should not pretend copy alone determines inbox placement. Sender setup still matters.

In a v1 copy review, a tool can safely flag:

• invalid or suspicious domain format
• missing sender domain input
• need to confirm SPF
• need to confirm DKIM
• need to confirm DMARC
• need to confirm From-domain alignment

It should not claim DNS certainty unless it actually resolves DNS.

What gets flagged: complaint math that feels small but is not

The number 0.3% sounds small. It is not small when you are sending volume.

That is why complaint budgeting belongs in the same workflow as copy review. A sequence that feels acceptable at 100 recipients can become dangerous at 5,000.

Run the math in the Email Complaint Rate Calculator.

A useful cold email spam checker should produce next actions

The score is not the product. The fix list is.

A serious checker should tell you:

• what to remove
• what to rewrite
• what to verify before sending
• which risks affect recipients
• which risks affect mailbox providers
• which risks are unknown because they were not checked

That last point matters. If DNS was not checked, the tool should say "not checked." Fake certainty is worse than no score.

The fastest self-check

Before using any tool, ask:

1. Is the sender identity clear?
2. Is the subject accurate?
3. Is the first line specific?
4. Is the value prop concrete?
5. Is there one CTA?
6. Is the opt-out path visible?
7. Is volume low enough to survive a bad test?
8. Are SPF, DKIM, and DMARC verified?

If you cannot answer those quickly, the message is not ready for volume.

Sources and next step

This guide references Google's sender requirements, Google's sender FAQ on spam rates and unsubscribe requirements, Google Postmaster Tools dashboards, Yahoo Sender Hub best practices, and the FTC's CAN-SPAM guide.

Paste a real draft into the AI Cold Email Deliverability Checker and fix the first three issues before sending.