How to meet Gmail, Yahoo and Microsoft sender requirements with Mautic

In 2024 Gmail and Yahoo turned a set of long-standing good practices into hard requirements for bulk senders, and Microsoft followed for Outlook.com in 2025. Since November 2025 Gmail has been rejecting non-compliant email outright, not just sending it to spam. If you send newsletters or campaigns from Mautic to more than a few thousand people a day, this guide is for you. It's a checklist you can work through in an afternoon.

Do the rules apply to me?

• Gmail counts you as a bulk sender once you send close to 5,000 messages a day to personal Gmail addresses. Subdomains count towards the same total, and once you're a bulk sender you stay one.
• Yahoo doesn't publish a number and looks at your domain and other signals.
• Microsoft applies its rules to senders of more than 5,000 messages a day to Outlook.com, Hotmail.com and Live.com addresses.

If you're anywhere near those numbers, work through this guide anyway. Everything here helps deliverability whatever your volume!

What they ask for

The providers do change things, so check their own pages from time to time.

Step 1. Authenticate your sending domain

Work through these three guides in order.

1. How to set up SPF for Mautic
2. How to set up DKIM for Mautic
3. How to set up DMARC for Mautic

When you're done, a test email from Mautic to Gmail should show SPF, DKIM and DMARC all as PASS under Show original, with DKIM signed by your own domain.

Step 2. Check every From address in Mautic

It's easy to authenticate one domain and forget an email that uses another. Check these places.

• The default From address in Settings > Configuration > Email Settings
• The Advanced tab of each email, where the From address can be overridden
• Any campaign or form actions that send email

Every domain you send from needs SPF, DKIM and DMARC.

While you're there, use a From and Reply-to address that someone actually reads, not noreply@. Replies are a good engagement signal, and people do reply to newsletters!

Step 3. Make sure one-click unsubscribe works

Mautic adds the one-click unsubscribe headers to marketing emails, but they only work when your DKIM signature covers them. Follow How to set up one-click unsubscribe in Mautic, and keep a visible unsubscribe link in every marketing email footer too. Put your postal address in the footer as well. It's a legal requirement in some countries, including under the US CAN-SPAM Act, and Yahoo points senders to it.

Step 4. Use transactional email only for transactional messages

Gmail exempts transactional messages (receipts, password resets) from the one-click unsubscribe requirement. Make sure your newsletters and promotions aren't set up as transactional emails. Providers look at the content, not the label.

Two that often get mixed up are welcome emails, which count as marketing even though a sign-up triggers them, and double opt-in confirmation emails, which are transactional.

Step 5. Keep complaints down

The spam complaint limit is where many senders come unstuck. Things that help most are these.

• Set up Google Postmaster Tools for your domain so you can see your complaint rate, and enrol in Yahoo's Complaint Feedback Loop.
• Stop mailing people who've stopped engaging. Ask inactive contacts whether they still want to hear from you, and stop mailing the ones who don't answer. See How to re-engage or sunset inactive contacts in Mautic.
• Process bounces, so dead addresses drop off your list. See How to handle email bounces in Mautic.
• Be clear at sign-up about what people will receive and how often, and use double opt-in on your Mautic forms.

Step 6. Check the results

• Send test emails to Gmail, Outlook.com and Yahoo addresses and check authentication in each (see How to check your email authentication in message headers).
• Check Postmaster Tools each week for the first month.
• Watch your DMARC reports for anything new sending as your domain.

Common problems

Rejections with 4.7.x or 5.7.x codes from Gmail. Gmail uses these codes for email that doesn't meet its requirements. Check authentication and unsubscribe headers first.

Everything passes, but email still goes to spam. Authentication gets you through the door, it doesn't guarantee the inbox. Look at your complaint rate, engagement and how old your segments are. The biggest lever is usually to stop sending to people who haven't engaged in months, see How to re-engage or sunset inactive contacts in Mautic. Recovering a damaged reputation takes weeks of consistent sending to engaged contacts, so be patient.

Moving to a new domain, IP address or email service. Mailbox providers don't know you yet. Start with small sends to your most engaged contacts and increase volume gradually over a few weeks, instead of sending to everyone on day one.

Using a marketing subdomain. Sending from news.yourdomain.com keeps marketing reputation separate from staff email, which is a good idea. Just remember Gmail adds subdomain volume to your main domain's total.

Over to you

Which of these requirements caused the most head scratching for you or your clients? I'd love to hear what tripped people up, so we can improve both these guides and Mautic's defaults.

References

Google Email sender guidelines. Google Workspace Admin Help. Available at https://support.google.com/a/answer/81126 (Accessed 26 October 2026).

Google Email sender guidelines FAQ. Gmail Help. Available at https://support.google.com/mail/answer/14229414?hl=en-GB (Accessed 26 October 2026).

Microsoft (2025) Strengthening email ecosystem: Outlook's new requirements for high-volume senders. Microsoft Tech Community. Available at https://techcommunity.microsoft.com/blog/outlook/strengthening-email-ecosystem-outlook%E2%80%99s-new-requirements-for-high%E2%80%90volume-senders/4399730 (Accessed 26 October 2026).

Yahoo Sender requirements and recommendations. Yahoo Sender Hub. Available at https://senders.yahooinc.com/best-practices (Accessed 26 October 2026).