What bulk senders must do
Gmail, Yahoo and Microsoft require senders of many mails to have SPF, DKIM, DMARC and one-click unsubscribe. If something is missing, mail lands in spam or is rejected.
How it works
Gmail and Yahoo have applied their rules since 2024, Microsoft (Outlook.com, Hotmail, Live) since 2025. A bulk sender is someone who sends about 5,000 or more mails a day to mailboxes of the respective provider. The basic rules, however, apply to all senders:
- SPF or DKIM for the sender domain.
- Valid reverse DNS for the sending servers: the IP address resolves to a name that leads back to this address.
- Encrypted sending with TLS.
- A low spam complaint rate: aim for below 0.1 %, never reach 0.3 %.
Bulk senders also need:
- SPF and DKIM, not just one of them.
- A DMARC record, at least with
p=none. The sender domain in the “From” field must match SPF or DKIM (alignment). - One-click unsubscribe for marketing and subscription mails: the headers
List-UnsubscribeandList-Unsubscribe-Post. Unsubscribes must be honoured within two days. - A visible unsubscribe link in the text of the mail.
If something is missing, the providers first throttle acceptance, sort mails into spam and finally reject them. The error messages usually name the missing piece.
What matters
- Alignment. If a service signs only with its own domain, it does not match the “From” field.
- Unsubscribe in the headers. A link in the text alone does not meet the rule for bulk senders.
- Complaint rate below 0.3 %. Above that, even clean technology does not help.
- The rules change. The providers' own sender guidelines are authoritative.
How to set it up
You enter SPF, DKIM and DMARC in the DNS settings of your domain. Reverse DNS is set by whoever runs the sending server, usually your mail or newsletter provider. One-click unsubscribe is switched on in your newsletter tool.
The domain check tests SPF, DKIM, DMARC and reverse DNS. One-click unsubscribe is in the headers of a mail; for that you need the test mail or the mail source check.