Summary
Emails sent via Mailchimp might not reach Microsoft inboxes for a multitude of reasons. These range from the recipient having blocked the sender, to Microsoft's complex and sometimes opaque filtering system, to issues with the sender's reputation (both IP and domain), to the content of the emails themselves, and poor list hygiene practices. Microsoft is known to sometimes accept emails only to discard them later. Proper authentication (SPF/DKIM) is critical, as is adhering to Microsoft's sending guidelines. Monitoring sender reputation, requesting mitigation from your ESP, cleaning email lists, segmenting content, using dedicated IPs (when appropriate), and setting up feedback loops are all important strategies. Furthermore, if an ESP can't provide rejection messages when asked, it may be time to switch providers.
Key findings
- Blocked Senders/Domains: Recipients may have explicitly blocked the sender or domain.
- Microsoft's Complex Filtering: Microsoft's filtering system is complex and can block emails even if they pass initial checks.
- Reputation is King: Microsoft heavily relies on sender reputation (both IP and domain).
- Content Matters: Email content can trigger spam filters.
- List Hygiene is Crucial: Poor list hygiene degrades sender reputation and deliverability.
- Vanishing Emails: Microsoft sometimes accepts emails but discards them silently.
Key considerations
- Check Blocked Lists: Recipients should check their blocked senders/domains lists.
- Request ESP Mitigation: Ask your ESP (Mailchimp) to investigate and mitigate reputation issues.
- Implement Authentication: Ensure SPF and DKIM are properly configured.
- Adhere to MS Policies: Adhere to Outlook.com's sending policies and guidelines.
- Practice List Hygiene: Regularly clean your email lists.
- Segment Content: Send targeted, relevant content to improve engagement.
- Monitor Reputation: Monitor your sender reputation (e.g., using SNDS).
- Consider Dedicated IPs: Consider a dedicated IP for high-volume sending with good reputation.
- Set Up Feedback Loops: Establish feedback loops to identify and address spam complaints.
- IP Warming: If using a new IP, gradually increase sending volume.
- Demand Transparency: Consider switching ESPs if they don't provide sufficient transparency (e.g., rejection messages).
- Escalate Issues: Escalate persistent issues with Microsoft support, providing details like 'd=' and selector values.
What email marketers say
11 marketer opinions
Emails sent via Mailchimp might not reach Microsoft inboxes due to various factors, including Microsoft's complex filtering system, reputation issues (IP or domain), email content triggering spam filters, and poor list hygiene. Microsoft sometimes "vanishes" emails after initial acceptance, and its filtering relies heavily on sender reputation. Senders should check spam folders, request ESP mitigation, maintain clean email lists, use targeted content, monitor IP reputation, consider dedicated IPs, and set up feedback loops.
Key opinions
- Reputation Matters: Microsoft heavily relies on sender reputation (IP and domain). Poor reputation may lead to blocked emails.
- Content Triggers: Email content (spam trigger words, excessive links, large images) can trigger spam filters.
- List Hygiene: Poor list hygiene (inactive or invalid email addresses) negatively impacts deliverability.
- Microsoft's Filtering: Microsoft's filtering system can be complex and might block emails even after initial acceptance.
- Vanishing Emails: Microsoft may accept emails but then effectively discard them.
Key considerations
- Check Spam Folders: Recipients should always check their spam/junk folders first.
- ESP Mitigation: Request your Email Service Provider (ESP) to mitigate reputation issues with Microsoft.
- Clean Email Lists: Regularly clean your email list to remove inactive or invalid addresses.
- Targeted Content: Segment your email lists and send targeted, relevant content to improve engagement.
- Monitor IP Reputation: Monitor your IP reputation using tools like Microsoft's Smart Network Data Services (SNDS).
- Dedicated IPs: Consider using a dedicated IP address, especially with high email volume.
- Feedback Loops: Set up feedback loops with Microsoft to identify and address deliverability issues based on spam complaints.
- IP Warming: Gradually increase email volume when using a new IP address to build reputation (IP warming).
Marketer view
Email marketer from EmailToolTester shares that setting up feedback loops with Microsoft can help identify and address deliverability issues. Feedback loops provide information about spam complaints from recipients.
19 Dec 2024 - EmailToolTester
Marketer view
Email marketer from Mailjet suggests gradually increasing email volume when using a new IP address (IP warming) to establish a good sending reputation with Microsoft.
11 May 2022 - Mailjet
What the experts say
7 expert opinions
Microsoft's email filtering system is complex and relies heavily on sender reputation. Emails sent via Mailchimp may be blocked even if they initially pass checks, and Microsoft sometimes accepts emails only to discard them later. Switching ESPs might not resolve the problem if the core issue is domain-based reputation. ESPs generally do not allow direct contact with Microsoft about shared IPs, though you can open a ticket. Monitoring sender reputation, ensuring high-quality content, and escalating issues with Microsoft are crucial. If an ESP cannot provide rejection messages, consider switching.
Key opinions
- Microsoft's Filtering Complexity: Microsoft's filtering system is complex and can block emails even after initial checks.
- Sender Reputation is Key: Microsoft heavily relies on sender reputation for deliverability.
- Vanishing Emails: Microsoft sometimes accepts emails only to discard them later.
- Domain Reputation Matters: If the problem is domain-based reputation, changing ESPs may not help.
- Limited ESP Cooperation: ESPs are unlikely to allow direct contact with Microsoft about shared IPs but can provide the IPs to make your own ticket.
Key considerations
- Monitor Sender Reputation: Actively monitor your sender reputation to identify and address issues.
- High-Quality Content: Ensure your email content is high quality and relevant to recipients.
- Escalate Issues: Escalate deliverability issues with Microsoft and emphasize emails disappearing after acceptance, providing relevant data like 'd=' and selector values.
- Demand Rejection Messages: If your ESP cannot provide rejection messages upon request, consider switching to a different ESP.
Expert view
Expert from Email Geeks notes that Microsoft sometimes accepts emails but then effectively discards them, causing them to disappear.
31 Oct 2022 - Email Geeks
Expert view
Expert from Email Geeks states that if an ESP cannot provide a rejection message upon request, it's time to consider switching to a different ESP.
13 Apr 2024 - Email Geeks
What the documentation says
5 technical articles
Emails may not reach Microsoft accounts due to being blocked, requiring recipients to check their blocked senders list. Proper email authentication (SPF, DKIM) is crucial. Adhering to Outlook.com's policies and maintaining a good sending reputation are essential. Using a dedicated IP can improve deliverability for high-volume senders. Utilizing Microsoft's Smart Network Data Services (SNDS) helps monitor IP reputation and identify issues.
Key findings
- Blocked Senders: Emails may be blocked if the sender or domain is on the recipient's blocked senders list.
- Authentication Matters: Proper email authentication (SPF, DKIM) improves deliverability.
- Outlook.com Policies: Following Outlook.com's policies and guidelines is essential for deliverability.
- Dedicated IPs Help: Using a dedicated IP address can improve deliverability for high-volume senders with good reputations.
- SNDS Monitoring: Microsoft's Smart Network Data Services (SNDS) helps monitor IP reputation.
Key considerations
- Check Blocked Lists: Recipients should check their blocked senders lists.
- Configure Authentication: Ensure SPF and DKIM are properly configured.
- Adhere to Policies: Adhere to Outlook.com's sending policies and best practices.
- Consider Dedicated IP: Consider using a dedicated IP if sending high volumes of email.
- Utilize SNDS: Use Microsoft's SNDS to monitor your IP reputation and identify deliverability issues.
Technical article
Documentation from Mailchimp shares that email authentication methods like SPF and DKIM are properly set up to improve deliverability. Mailchimp provides instructions on how to configure these settings.
6 Aug 2021 - Mailchimp
Technical article
Documentation from SparkPost explains that using Microsoft's Smart Network Data Services (SNDS) allows senders to monitor their IP reputation and identify potential issues affecting deliverability to Microsoft accounts.
13 Jan 2024 - SparkPost
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