The following is a summary of best practices for sending email to Microsoft users. Microsoft recommends following their best practice guidelines to help avoid deliverability issues.
Resources
- Microsoft Postmaster
- Microsoft Junk Mail Reporting Program (JMRP)
- Microsoft Smart Network Data Services (SNDS)
Best practices
- Reputation
- Sign up with Microsoft’s Junk Mail Reporting Program (JMRP) and immediately suppress all complainers from receiving future emails.
- High complaint rates harm your sending reputation and can result in more messages marked as spam.
- Sign up with Microsoft’s Smart Network Data Services (SNDS) to help troubleshoot delivery and sending reputation problems.
- Validity Certified senders should monitor Sender Reputation Data (SRD) in Everest. SRD junk votes are weighted heavily in Microsoft's filter decisions.
- Sign up with Microsoft’s Junk Mail Reporting Program (JMRP) and immediately suppress all complainers from receiving future emails.
- Sending guidelines
- Encourage recipients to add your sending address to their safe senders list. Email addresses in the safe sender's list bypasses the SmartScreen filter and is delivered to the inbox.
- Set proper expectations about the content and frequency of your email. If possible, use a preference center.
- Send messages no larger than 25 MB.
- Infrastructure
- Follow all Internet and SMTP standards.
- Do not send email through an open relay or open proxy server. Make sure all email sent from your servers is authorized.
- Do not send email from a dynamic IP address.
- Ensure your IP address (IPv4 or IPv6) has a valid, non-generic rDNS (PTR) record.
- Do not open more than 500 simultaneous connections to Microsoft email servers. Send no more than 50 messages per connection.
- Microsoft may adjust your connection and throughput based on your sending reputation. Monitor your SMTP error codes for deferral messages and adjust accordingly.
- Opt-in consent
- Use opt-in consent methods.
- Do not purchase lists or engage in list harvesting techniques from websites and social networks.
- List hygiene
- Ensure you have good list hygiene practices and remove inactive subscribers regularly.
- Identify when subscribers typically stop engaging with your email and send them a win-back email.
- If subscribers continue to be unengaged with your email, consider sending them a re-confirmation email before adding them to your suppression list.
- Authentication
- Authenticate all email using Sender Policy framework (SPF), DomainKeys Identified Mail (DKIM), and Domain-based Message Authentication, Reporting, and Conformance (DMARC).
- Work towards a quarantine or reject DMARC policy to help protect your brand from unauthorized use of your domain.
- Authenticate all email using Sender Policy framework (SPF), DomainKeys Identified Mail (DKIM), and Domain-based Message Authentication, Reporting, and Conformance (DMARC).
- Unsubscribe
- Include a prominent unsubscribe link in all emails and immediately honor all unsubscribe requests.
- Use the list-unsubscribe header with the mailto: option in all email streams.
- If you do not use the mailto: option, Microsoft will give your subscribers an option to block your future email messages.
- Using the mailto: option will give your subscriber an option to unsubscribe from your email instead of blocking you, and future messages will be placed in the spam folder. Be sure to immediately honor all unsubscribe requests once received.
- Engagement
- Send to people that want to receive your email. Highly engaged subscribers improves your sending reputation and can lead to higher inbox placement.
- For subscribers with the Microsoft Focused Inbox activated, senders with email deemed more important through higher engagement are placed in the Focused Inbox instead of the Other Inbox.
- Send to people that want to receive your email. Highly engaged subscribers improves your sending reputation and can lead to higher inbox placement.
- Content
- Do not use scripting languages in email design such as ActiveX or JavaScript.
- Always include valid, reputable URLs in your email content. Do not link to known phishing websites. Microsoft doesn’t publicly disclose how they identify dangerous websites, but you can check:
- Use the standard URL format. Avoid using IP addresses in the URL.
- Clearly brand email with a recognizable friendly-from address so that recipients are able to easily identify you.
- Avoid excessively urgent calls to action, such as Must sign up today!, Log in right now!, and Update immediately!. These are commonly used by spammers and could contribute to deliverability problems with Microsoft. Using urgency in your calls to action such as Buy now, Download our app, Start saving, Get your coupon, Learn more, and Shop now is a best practice, so try testing variations of your call-to-action to find out what resonates with your subscribers.
- Review your SMTP error codes frequently
- If you start to see 4xx deferral messages from Microsoft, Microsoft recommends that you stop all sending from that IP address for at least one hour and resume sending at a slower rate. If the deferral messages continue after you resume sending, stop sending from that IP for at least 24 hours.
- Refer to Microsoft's SMTP error codes for additional information related to the deferral messages.
- Investigate and fix the cause of the deferral messages. You especially want to be sure they are not caused by unauthorized access to your IP address.
- If you continue to send at a high rate when seeing the deferral messages, it can negatively impact your sending reputation, which may lead to a decrease in inbox placement.
- Do not resend a message to an email address returning a non-delivery error code between 500 and 599.
- Do not send email to an address returning multiple non-delivery responses.
- Immediately unsubscribe and suppress email addresses that return an SMTP error code indicating the address is an unknown user or inactive account.
- If you start to see 4xx deferral messages from Microsoft, Microsoft recommends that you stop all sending from that IP address for at least one hour and resume sending at a slower rate. If the deferral messages continue after you resume sending, stop sending from that IP for at least 24 hours.
- Onboarding new IP addresses or domains
- Warm up new IP addresses and domains and make sure to update your Junk Email Reporting Program (JMRP) account to receive complaint feedback.
- New IP addresses using the same Return-path domain inherits the domain reputation, which can help with the warm up process if you have a good domain reputation.
- Notify Microsoft in advance of any new IP warming activities.
- Warm up new IP addresses and domains and make sure to update your Junk Email Reporting Program (JMRP) account to receive complaint feedback.
- Onboard new subscribers into your marketing email stream
- New subscribers are people that have recently opted-in to receive your email and have not received previous marketing email from you.
- Send a welcome email to all new subscribers. It is best to trigger a welcome email to a new subscriber once they have opted in. However, if you send a bulk welcome message to multiple new subscribers at the same time, split up the send in small batches and send over a period of time instead of all at once.
- If you don't send a welcome message and just add new subscribers to your regular day-to-day marketing email stream, ensure that new Microsoft subscribers do not exceed 5% of the total Microsoft subscribers on any particular send.
- For example, if you are sending to 100000 Microsoft subscribers for a single campaign, make sure that new Microsoft subscribers do not exceed 5000.
- Split up your campaigns if your new Microsoft subscribers exceed 5%.