How to prevent Microsoft 365 from blocking outbound business development emails?

Summary

Preventing Microsoft 365 from blocking outbound business development emails requires a multi-faceted approach focused on authentication, sender reputation, and recipient engagement. It is vital to understand that Microsoft prioritizes its users' experience and filters emails that are deemed unwanted or spam. Strong authentication using SPF, DKIM, and DMARC is crucial. Building and maintaining a positive sender reputation involves warming up IP addresses, sending relevant and personalized content, segmenting email lists, cleaning inactive addresses, and obtaining explicit opt-in. Continuous monitoring of sender reputation, bounce rates, spam complaints, and adherence to sending limits is essential. Additionally, the email content must provide value and respect recipient preferences, ensuring easy unsubscribe options and prompt removal of unsubscribed users. Cold emailing without consent is generally discouraged and can lead to blocking.

Key findings

  • Authentication is Key: Properly configured SPF, DKIM, and DMARC are foundational to email deliverability.
  • Sender Reputation Matters: Building and maintaining a good sender reputation significantly reduces the risk of being blocked.
  • Engagement is Crucial: High recipient engagement (opens, clicks) and low spam complaints improve deliverability.
  • Content Relevance is Important: Personalized and valuable content is less likely to be flagged as spam.
  • Consent is Necessary: Obtaining explicit opt-in ensures recipients want to receive your emails.

Key considerations

  • Policy Compliance: Adhere to Microsoft's sending policies and acceptable use guidelines.
  • Reputation Management: Actively monitor and manage your IP and domain reputation using available tools.
  • List Hygiene: Regularly clean your email lists to remove inactive or invalid addresses.
  • Testing and Monitoring: Test email deliverability and monitor campaign performance to identify and address issues.
  • Respect Recipient Preferences: Provide easy unsubscribe options and honor unsubscribe requests promptly.

What email marketers say
7Marketer opinions

To prevent Microsoft 365 from blocking outbound business development emails, several strategies should be implemented. These include warming up IP addresses, segmenting email lists, personalizing email content, cleaning email lists of inactive addresses, and employing double opt-in processes. Maintaining a dedicated IP, monitoring sender reputation, using consistent sending volumes, respecting unsubscribe requests, and ensuring emails provide value are also crucial. Additionally, setting up proper email authentication (SPF, DKIM, DMARC) and regularly testing email deliverability are recommended.

Key opinions

  • IP Warmup: Gradually increase sending volume to build a positive reputation with ISPs.
  • List Segmentation: Segment your audience to send relevant emails, improving engagement and reducing spam reports.
  • Personalization: Personalize email content to increase engagement and avoid spam filters.
  • List Hygiene: Regularly clean email lists to remove inactive or invalid addresses, improving sender reputation.
  • Dedicated IP: Use a dedicated IP address to protect sender reputation.
  • Reputation Monitoring: Monitor IP and domain reputation using tools like Google Postmaster Tools.
  • Consistent Volume: Maintain a consistent sending volume to avoid triggering spam filters.
  • Double Opt-in: Implement double opt-in to ensure subscribers actively want to receive emails.
  • Value-Driven Content: Ensure emails provide value and are tailored to individual needs.

Key considerations

  • Sender Reputation: Maintaining a positive sender reputation is critical for deliverability.
  • Email Authentication: Implement SPF, DKIM, and DMARC to authenticate your emails.
  • Engagement Metrics: Monitor bounce rates and spam complaints to identify and address issues.
  • Testing: Test email deliverability before sending campaigns using tools like Mail-Tester.
  • Unsubscribe Handling: Respect unsubscribe requests promptly to maintain compliance and sender reputation.
Marketer view

Email marketer from EmailonAcid shares that list segmentation is an effective method to improve deliverability. You can send emails to the right people, at the right time. Another factor is personalizing emails as it has a better chance of not being marked as spam.

January 2022 - EmailonAcid
Marketer view

Email marketer from Woodpecker.co explains that you need to ensure you are using a dedicated IP address for sending your email, this will help protect your reputation. Create a separate domain used just for email campaigns. Avoid using URL shorteners as they are commonly used by spammers.

September 2021 - Woodpecker.co
Marketer view

Email marketer from Sendinblue shares that warming up your IP address is crucial when starting new campaigns. Gradually increase sending volume to build a positive reputation with ISPs. Furthermore, segment your audience and personalize your messages to improve engagement and reduce the likelihood of being marked as spam.

November 2022 - Sendinblue
Marketer view

Email marketer from Reddit suggests ensuring your cold emails provide value to the recipient and are highly personalized. Avoid generic templates and tailor your message to each individual's needs and interests. Respect unsubscribe requests promptly and avoid sending follow-up emails to those who have opted out.

November 2022 - Reddit
Marketer view

Email marketer from Mailjet suggests cleaning your email lists regularly to remove inactive or invalid addresses, as sending to these can negatively impact your sender reputation. They suggest using a double opt-in process to ensure subscribers actively want to receive your emails, which helps reduce spam complaints. Monitor your bounce rates and spam complaints to quickly identify and address any issues.

October 2024 - Mailjet
Marketer view

Email marketer from StackOverflow advises closely monitoring your IP and domain reputation using tools like Google Postmaster Tools. Address any negative feedback or reputation issues promptly to maintain good sending health. Use a consistent sending volume and avoid sudden spikes, which can trigger spam filters.

January 2025 - StackOverflow
Marketer view

Email marketer from Gmass explains that sending personalized emails is key to avoiding spam filters. They also suggest testing your email using a tool like Mail-Tester before sending your email campaigns.

March 2024 - Gmass

What the experts say
4Expert opinions

To prevent Microsoft 365 from blocking outbound business development emails, understanding the perspective of mailbox providers like Microsoft and Gmail is crucial. Microsoft blocks senders for violating their acceptable use policy and deeming emails as spam based on outbound filters. Building and maintaining a good sender reputation through managing IP and domain reputation, improving engagement metrics, and segmenting email lists is important. Proper email authentication with SPF, DKIM, and DMARC is essential, alongside ensuring explicit authorization to send emails by capturing opt-in correctly and only sending desired content. Avoid practices considered spam, such as cold emailing without consent, as most ESPs and deliverability consultants also advise against it.

Key opinions

  • Mailbox Provider Perspective: Microsoft and other mailbox providers block emails they deem spam or in violation of their policies, regardless of the sender's intent.
  • Sender Reputation: Building and maintaining a good sender reputation is essential for deliverability.
  • Email Authentication: Properly configure SPF, DKIM, and DMARC to authenticate your emails.
  • Authorization: Ensure you have explicit permission (opt-in) to send emails.
  • Cold Emailing Risks: Cold emailing without consent is often considered spam and can lead to blocking.

Key considerations

  • Policy Compliance: Understand and adhere to Microsoft 365's acceptable use policies to avoid triggering outbound filters.
  • Reputation Management: Actively manage IP and domain reputation by monitoring engagement metrics and addressing negative feedback.
  • List Segmentation: Segment email lists to send relevant content to engaged subscribers, reducing the risk of spam complaints.
  • Opt-in Practices: Implement clear and explicit opt-in processes to ensure recipients want to receive your emails.
  • ESP Limitations: Recognize that most ESPs prohibit cold emailing and will terminate accounts that engage in such practices.
Expert view

Expert from Word to the Wise explains that you need to focus on building and maintaining a good sender reputation, which includes managing your IP address reputation, domain reputation, and engagement metrics. Ensure your sending infrastructure is properly configured with SPF, DKIM, and DMARC. Also, segment your list to send relevant emails to engaged subscribers, and avoid sending to inactive or unengaged recipients.

March 2023 - Word to the Wise
Expert view

Expert from Email Geeks shares that it doesn't matter if we think cold leads are spam; it's what the mailbox provider thinks. This is why Gmail puts them in the spam folder so often. In this case, there was enough unwanted activity to cause Microsoft to shut it off on the outbound side as they felt it was spam.

September 2022 - Email Geeks
Expert view

Expert from Word to the Wise shares you need to ensure proper authentication with SPF, DKIM and DMARC. Authorization is ensuring you have permission to send them mail, by capturing opt-in correctly, and only sending them mail they want.

August 2024 - Word to the Wise
Expert view

Expert from Email Geeks explains that the user has triggered Microsoft's outbound filters and that Microsoft sees the mail as spam and is violating their acceptable use policy. Most ESPs also won't let you cold email off of their platforms because they see the mail as spam. Many recipients also hate the mail and regularly report it, filters will block it because users see it as spam. Most deliverability consultants also won't work with people who are sending cold email because it's not opt-in.

May 2024 - Email Geeks

What the documentation says
5Technical articles

To prevent Microsoft 365 from blocking outbound business development emails, a strong emphasis is placed on proper email authentication using SPF, DKIM, and DMARC records. These records authorize sending mail servers, verify email authenticity, and instruct receiving servers on how to handle emails that fail authentication checks. Maintaining a good sender reputation by avoiding unsolicited emails, providing easy unsubscribe options, and monitoring for suspicious activity is crucial. Following sending limits, using TLS connections, tracking sender reputation via Google Postmaster Tools, and checking for domain/IP blocklisting are also recommended. A gradual approach to DMARC policy implementation, starting with monitoring and progressing to stricter enforcement, is advised.

Key findings

  • SPF, DKIM, DMARC: Properly configuring SPF, DKIM, and DMARC is essential for email authentication.
  • Sender Reputation: Maintaining a good sender reputation helps avoid being blocked.
  • Monitoring: Monitoring outbound email activity, sender reputation, and DMARC reports helps identify and address issues.
  • Compliance: Following sending limits and policies set by Microsoft 365 is necessary.
  • TLS Encryption: Using TLS connections ensures secure email transfer.

Key considerations

  • Authentication Validation: Validate SPF records using online tools to ensure correct configuration.
  • Key Rotation: Rotate DKIM keys periodically to maintain security.
  • DMARC Gradual Implementation: Start with a DMARC policy of 'p=none' and gradually move to stricter policies.
  • Blocklist Monitoring: Regularly check if your domain or IP is on any blocklists.
  • Unsolicited Email: Avoid sending unsolicited email to maintain sender reputation.
Technical article

Documentation from DMARC.org shares that a DMARC policy tells receiving mail servers what to do with emails that fail SPF and DKIM checks. They suggest starting with a policy of 'p=none' to monitor email flows and gradually move to stricter policies like 'p=quarantine' or 'p=reject' as you gain confidence in your email authentication setup. Regularly review DMARC reports to identify and address any authentication issues.

March 2025 - DMARC.org
Technical article

Documentation from Google Workspace Admin shares that you need to authenticate your email. Make sure you are setting up SPF, DKIM and DMARC records. Use a TLS connection to ensure emails are secured during transfer. Keep your sending rate within limits. Monitor your sender reputation using Google Postmaster Tools. Check if your domain or IP is on any blocklists.

October 2023 - Google Workspace Admin
Technical article

Documentation from Microsoft explains that the SPF record needs to be added to your domain's DNS records to authorize sending mail servers. They share how to construct the SPF record to include all valid sending sources for your domain, including third-party senders. Validate your SPF record using online tools to ensure it's correctly configured.

June 2024 - Microsoft
Technical article

Documentation from Microsoft shares that enabling DKIM signing for your domain adds a digital signature to your outbound emails, verifying their authenticity. They detail the steps to generate DKIM keys and configure DNS records for Microsoft 365. Rotate your DKIM keys periodically to maintain security and prevent unauthorized use.

May 2022 - Microsoft
Technical article

Documentation from Microsoft Support explains that to avoid being blocked, ensure your domain is properly authenticated with SPF, DKIM, and DMARC records. Maintain good sender reputation by avoiding sending unsolicited email and ensuring recipients can easily unsubscribe. Also, monitor your outbound email for suspicious activity and follow Microsoft 365's sending limits and policies.

April 2022 - Microsoft Support

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