Gmail, Yahoo and Microsoft sender requirements

What Google requires, with the source on every row

Google splits its guidelines into requirements for all senders and additional requirements that apply from 5,000 messages a day to Gmail accounts. The FAQ is explicit about how that count works: "all messages sent from the same primary domain count toward the 5,000 limit".

Where the 2% and 5% figures actually come from

This is the part nobody writes, and it is the reason this page exists. No mailbox provider publishes a bounce-rate threshold. Not Google, not Yahoo, not Microsoft. Read all three published pages end to end — they are linked at the foot of this page — and the number is not there, because bounce rate is not the metric any of them has written a rule about.

So the figures come from the other side of the send: email service providers, who suspend and throttle accounts under their own acceptable-use policies. That is a real consequence with real money attached. It is simply not the rule the receiving side is applying.

And here is the uncomfortable second half, which we checked rather than assumed: the ESPs mostly do not publish a number either. Mailchimp’s own suspension page says only that "If abuse complaints exceed our threshold, we'll send you a warning notice. If the abuse rate is far beyond that threshold, we'll send you a suspension notice" — and never states what the threshold is. Their acceptable-use policy states no percentage either. Both read 11 September 2026.

Which means the honest account of "keep bounces under 2%, never above 5%" is: an industry rule of thumb, widely repeated, not traceable to a published policy at either the mailbox provider or — in the case we checked — the ESP. It is still useful. A list bouncing at 5% is a bad list and the number tells you so. It is just not a rule anybody wrote down, and every article presenting it as Gmail policy is repeating something it did not check.

Why bounce rate still matters, stated precisely

A high bounce rate is a leading indicator of the metrics that are under policy, not a metric under policy itself. A list producing many hard bounces was built badly — bought, scraped, or left to age — and a list built badly also produces spam complaints, hits spam traps, and shows poor engagement. Those are the things providers measure.

So the correct sentence is "keep bounces low because they reflect how the list was built", not "keep bounces under 5% because Gmail says so". Gmail does not say so. The bounce rate page has the arithmetic and the same sources.

Yahoo

Yahoo’s Sender Hub best practices require bulk senders to "Implement both SPF & DKIM" and to "Publish a valid DMARC policy with at least p=none - DMARC must pass", and to "Implement a functioning list-unsubscribe header, which supports one-click unsubscribe for marketing and subscribed messages".

On complaints Yahoo publishes one number and it is different from Google’s headline figure: "Keep your spam rate below 0.3%". Note that this is Yahoo’s stated requirement rather than Google’s stricter 0.10% target, so a sender sitting at 0.2% is inside Yahoo’s published line and outside Google’s. Yahoo publishes no bounce-rate threshold, and this page will not invent one on their behalf.

Microsoft

Microsoft announced its own high-volume sender requirements on 2 April 2025, for Outlook.com, Hotmail and Live consumer addresses. The threshold is the same shape as Google’s: "domains sending more than 5,000 emails per day".

• —SPF — "Must Pass for the sending domain."
• —DKIM — "Must Pass to validate email integrity and authenticity."
• —DMARC — "At least p=none and align with either SPF or DKIM (preferably both)."
• —Recommended alongside those: a replyable From or Reply-To address, functional unsubscribe links, and list hygiene — Microsoft’s own wording is "Remove invalid addresses regularly to reduce spam complaints, bounces, and wasted messages".

The enforcement note is worth reading carefully, because the post was updated and both versions are still on the page. Non-compliant mail from high-volume domains is routed to Junk from 5 May 2025, and the post also states that rejected messages carry 550; 5.7.515 Access denied, sending domain [SendingDomain] does not meet the required authentication level, with outright rejection announced for a date to be confirmed. If you are seeing that code, the SMTP reply reference has the rest of the family.

Microsoft publishes no complaint-rate and no bounce-rate threshold in that announcement. Three providers, three published rule sets, and not one bounce-rate number between them.

What to do about it

1. 1.Check SPF, DKIM and DMARC on the sending domain, and check that the From domain aligns with one of them. The SPF, DKIM and DMARC checker does all three at once, free and without an account.
2. 2.Add List-Unsubscribe and List-Unsubscribe-Post headers so one-click unsubscribe works, and keep the visible link as well — Google requires both.
3. 3.Watch the spam rate in Google Postmaster Tools, because that is the number with a published threshold behind it. Nobody publishes your bounce rate back to you; the complaint rate they do.
4. 4.Verify the list close to the send rather than on a calendar. Bulk verification prices on unique addresses and shows the cost before anything is charged.
5. 5.Remove every undeliverable permanently. Retry unknown later. Do not delete an unknown — the mailbox was never tested, and deleting it removes real customers with no signal that it happened. The unknown verdict page has the full table of what produces one.

Terms used on this page

• Bounce rateWhat is a good email bounce rate?
• Sender reputationWhat is sender reputation?
• Spam trapWhat is a spam trap?
• Email list hygieneWhat is email list hygiene?