It was back in 2023 when Google and Yahoo simultaneously announced that they would start penalizing senders who did not follow their guidelines. The announcement caused some panic because many domains didn’t have DMARC records, some ESPs only DKIM signed messages with a shared domain, and many ESPs did not support RFC 8058 which describes the required one-click unsubscribe mechanism.
Now in 2026 the dust has settled and other providers have since announced enforcement of their own bulk sender requirements to little fanfare; mainly because all of the heavy lifting was done achieving compliance with Google and Yahoo.
Following is a summary of the key sender requirements for the four main consumer mailbox providers as of September 2026.
| Yahoo | Microsoft | Apple | ||
|---|---|---|---|---|
| Bulk definition | 5,000+ messages/day | N/A | 5,000+ messages/day | N/A |
| Scope | Gmail.com and Googlemail.com | Everything except yahoo.co.jp | Outlook.com and legacy MS domains like hotmail.com | iCloud.com |
| Unsolicited mail | Not permitted | Not recommended | N/A | Not permitted |
| Unsubscribe Link | Required | Required | Required | Required |
| One-Click Unsubscribe | Required | Recommended | N/A | N/A |
| Working From/Reply-To | Required | N/A | Required | N/A |
| SPF | Required | Required | Required | Required |
| DKIM | Required | Required | Required | Required |
| DMARC | Required and must pass (p=none is fine) | Required and must pass (p=none is fine) | Required and must pass (p=none is fine) | Required and must pass (p=none is fine) |
| FCrDNS | Required | Required | Required | Required |
| Complaint Rate | Ideally below 0.10%, never exceeding 0.30% | Below 0.30% | N/A | N/A |
| Link to requirements | here and more information here | here and more information here | here | here |
You can see that the requirements are broadly the same across the board and being in compliance with Google more than likely means that you are in compliance with everyone, including providers outside of the ones listed above.
The above is a summary only and I would advise anyone intending to send bulk emails to read the complete requirements for each provider.
More than one of the requirements make reference to Sender Best Common Practices (Version 3.0) produced by the Messaging, Malware and Mobile Anti-Abuse Working Group (M3AAWG) industry group which is definitely worth familiarizing yourself with in addition to provider requirements.