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Validation statuses

How to approach your validation results?

Written by Sasha Dolishchuk
Updated today

What the statuses really mean

  • Valid: The address looks good and should receive mail just fine. This is your safest bucket.

  • Catch-all: The domain accepts everything, so the verifier can't tell if this exact inbox is real. Some will work, some will bounce.

  • Invalid: These are dead or broken addresses. If you send here, you're basically asking for hard bounces.

  • Unknown: The checker couldn't get a clear answer (timeouts, security filters, etc.). Some are fine, some aren't - it’s a "shrug" bucket.

In short:

  • Valid = go.

  • Catch-all = proceed very carefully.

  • Invalid, Unknown = don't touch.

What "Outlook with/without protection" and "Google + custom" mean

  • Outlook without protection

    • Mail is hosted on Microsoft 365, filtered mostly by Microsoft itself.

    • Still strict, but you're dealing mainly with the built‑in Microsoft filters and reputation rules.

  • Outlook with protection

    • Outlook sits behind an extra security layer like Mimecast, Proofpoint, Barracuda, Cisco, etc.

    • These guys are picky: they really don't like spikes, bad lists, or unknown senders, or anything else the recipient sets up manually.

  • Google + custom

    • Gmail/Google Workspace, sometimes with a bit of extra routing or filtering around it.

    • Google leans hard on engagement: opens, clicks, replies, spam complaints, and sending patterns.

In short:

  • "With protection" = extra guard dog at the door.

  • "Without protection" or "Google + custom" = still guarded, but more directly by Microsoft or Google.

How to treat each group

Valid

  • Outlook without protection/ Google + custom

    • Use this as your main volume

    • Still ramp sensibly and keep content relevant so ESPs see good engagement.

    • Good targeting and quick suppression of dead weight are key.

  • Outlook with protection

    • Keep all the previous recommendations.

    • Add carefully: couple per your batch, as it's likely you won't get through their guard dog.

Catch-all

  • Outlook without protection/ Google + custom

    • Add these once your Valid sending is stable and healthy.

    • Add a couple per batch and immediately drop anything that hard-bounces.

  • Outlook with protection

    • This is where you really need to be EXTRA careful.

    • Either send a tiny bit, and only if your bounce rate is very low, or skip them if you can.

Unknown

  • Outlook without protection / Google + custom

    • Treat it as an experiment bucket. Never rely on getting results from them. Either send a tiny bit, and only if your bounce rate is very low, or skip them if you can.

  • Outlook with protection

    • Very risky, usually not worth pushing hard.

Invalid

  • Just suppress them.

  • Sending to invalids is one of the fastest ways to hurt your domain and IP reputation.

What’s safest to send (ranked)

From safest to riskiest combo:

  1. Valid + Outlook without protection/ Google + custom

  2. Valid + Outlook with protection

  3. Catch-all + Outlook without protection/ Google + custom

  4. Catch-all + Outlook with protection

  5. Unknown + Outlook without protection / Google + custom

  6. Unknown + Outlook with protection

  7. Invalid + anything

Why:

  • Valid is always your cleanest technical bet.

  • Catch-all adds bounce risk, so you have to go slower.

  • Unknown is even more of a gamble - we don't recommend these, so you can try them at your own risk.

  • Invalid is pure trouble - guaranteed to drag down your reputation.

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