The requirements from Gmail, Yahoo, and Microsoft for those who send a lot of mail
Gmail, Yahoo and Microsoft (Outlook.com, Hotmail, Live.com and MSN) together receive a large share of all personal mail. Since February 2024, Google and Yahoo have set fixed requirements for anyone sending mail to their users. Microsoft has done the same since 2025 for Outlook.com and its other consumer addresses. If you send a lot of mail, for example a newsletter, extra requirements apply to you. In this article you can read what these requirements are and what they mean for you.
Requirements for everyone
Even if you only send a few emails a day, Gmail and Yahoo expect this:
- SPF or DKIM: at least one of the two checks must pass. SPF is the list of servers allowed to send mail on behalf of your domain, DKIM is a digital signature under each email.
- Reverse DNS (PTR): the IP address of the sending server has a name that points back to the same IP address.
- TLS: the connection to the recipient is encrypted (Gmail).
- Few complaints: less than 0.3% of your mail is marked as spam by recipients.
- Properly formed messages according to the standard, for example exactly one sender in the From line.
Reverse DNS and TLS are arranged by the party managing the sending server. SPF, DKIM and DMARC are set in your domain's DNS. Always use an address on your own domain as the sender, never a @gmail.com address through another server: that fails DMARC.
Extra requirements if you send a lot
Google calls you a bulk sender if you send around 5,000 emails or more to personal Gmail addresses within 24 hours. Mail from subdomains counts towards your main domain. Once you've reached that threshold, you remain a bulk sender. Microsoft also applies 5,000 emails per day with the same domain in the From line. Yahoo doesn't state a fixed number.
For bulk senders, the following is added:
- SPF and DKIM, not just one of the two. Microsoft requires both to pass.
- A DMARC record, at least
p=none. Stricter is allowed. Read What is DMARC? Explained in plain language. - Alignment: the domain in the From line matches the domain for which SPF or DKIM passes. In short: the mail must pass DMARC.
- One-click unsubscribe in marketing and subscription mail, plus a visible unsubscribe link in the text. You must process unsubscribes within 2 days. Read One-click unsubscribe: the List-Unsubscribe header.
- Complaints below 0.3%, and preferably below 0.1%. That's one complaint per thousand emails.
Error messages you might encounter
If your mail doesn't comply, the recipient may temporarily or permanently reject it, or send it to spam. A code starting with 4 is temporary, one starting with 5 is permanent.
| Code | From | Meaning |
|---|---|---|
550 5.7.26 | Gmail | The sender isn't authenticated: SPF and DKIM fail, or DMARC fails. |
550 5.7.25 | Gmail | The sending IP address has no reverse DNS. |
550 5.7.27 and 550 5.7.30 | Gmail | SPF failed, or DKIM failed. |
421 4.7.32 | Gmail | The From domain isn't aligned. Gmail is temporarily throttling. |
550 5.7.515 | Microsoft | You're sending a lot to Outlook.com, and SPF or DKIM fails, or DMARC is missing. |
550 5.7.509 | Microsoft | The mail doesn't pass DMARC and your own policy is set to p=reject. |
Got a message like this back? In My email doesn't arrive or ends up in spam: how to find out why you can read how to find the cause.
What does this mean if your mail is hosted with WebOké?
If your domain's DNS is hosted with WebOké, then SPF, DKIM and DMARC for regular mail from your hosting package are set correctly by default. The DMARC record for a hosting package is v=DMARC1;p=reject, which is stricter than the requirement. With the Email check or the card Set up email (MX, SPF, DKIM, DMARC) in My WebOké, you can see whether everything is correct.
With a hosting package you won't reach 5,000 emails a day: a sending limit applies, 300 emails per day per package by default. Read Sending limits and the 'message limit reached' notification. If you want to send a newsletter to many people, use a newsletter service instead. Such a service adds the unsubscribe headers itself, handles bounces and complaints, and shows you your complaint rate. Also read Can I send a mailing through my hosting package at WebOké?
p=reject and the service isn't set up correctly yet, your newsletter will be rejected. See Adding or changing an SPF record in DirectAdmin and Setting up DKIM when DNS is hosted elsewhere.Measuring it yourself
In Google Postmaster Tools, after confirming your domain with a TXT record, you can see your complaint rate and whether your mail passes SPF, DKIM and DMARC. You'll only see figures once you send enough mail to Gmail. If you send through a newsletter service, that service usually shows the complaint rate per send itself.