Summary
Recruitment emails to higher education institutions are frequently marked as spam in Office 365 due to a multifaceted interplay of factors, including the adaptive and stringent nature of Office 365's spam filters, the sender's IP address and domain reputation, email content and engagement metrics, and the proper configuration of email authentication protocols. A poor IP reputation stemming from prior spam activity or blocklisting significantly increases the likelihood of emails being flagged. Additionally, low engagement rates (opens, clicks), high bounce rates, and spam complaints negatively impact sender reputation. Generic or unsolicited content also contributes to deliverability issues. Proper sender authentication using SPF, DKIM, and DMARC is crucial for verifying sender identity and preventing spoofing. Maintaining list hygiene by removing inactive subscribers and gradually warming up IP addresses are essential for establishing a positive sender reputation. Office 365 leverages Spam Confidence Levels (SCL), with high SCL scores potentially leading to emails being dropped or filtered.
Key findings
- Adaptive Spam Filters: Office 365 employs sophisticated and constantly evolving spam filters.
- Sender Reputation: A poor sender reputation, influenced by low engagement, high bounce rates, and spam complaints, greatly impacts deliverability.
- Email Authentication: Properly configuring SPF, DKIM, and DMARC is vital for authenticating emails and improving deliverability.
- IP Reputation Importance: IP address reputation significantly affects deliverability; a history of spam activity can lead to emails being flagged.
- Content Relevance: Unsolicited or generic content is more likely to be classified as spam.
- SCL Scoring: Office 365 uses Spam Confidence Levels (SCL) to determine the likelihood of a message being spam, with high SCL scores resulting in filtering or rejection.
Key considerations
- Implement Email Authentication: Ensure SPF, DKIM, and DMARC are correctly configured to verify sender identity and enhance deliverability.
- Monitor IP Reputation: Regularly monitor and maintain your IP address reputation to prevent it from being blocklisted.
- Improve Engagement: Enhance email engagement by personalizing content, segmenting your audience, and optimizing send times.
- List Hygiene: Practice good list hygiene by removing inactive subscribers and managing bounce rates effectively.
- IP Warm-up: Gradually warm up new IP addresses to establish a positive sending reputation before sending high volumes of emails.
- Dedicated IP Address: Consider using a dedicated IP address to build and maintain your own sender reputation, especially for high-volume sending.
What email marketers say
9 marketer opinions
Recruitment emails to higher education institutions are often marked as spam in Office 365 due to a combination of factors related to sender reputation, email content, and technical configurations. Poor sender reputation stems from low engagement rates (opens, clicks), high bounce rates, spam complaints, or being listed on blocklists. Content that is perceived as unsolicited or generic also contributes to emails being flagged as spam. Additionally, not properly configuring email authentication protocols (SPF, DKIM, DMARC) can hinder deliverability. Strategies to improve deliverability include maintaining good list hygiene, using a dedicated IP address, warming up the IP address gradually, personalizing email content, and optimizing send times.
Key opinions
- Sender Reputation: Low engagement, high bounce rates, and spam complaints negatively impact sender reputation, causing emails to be flagged as spam.
- Email Authentication: Improper configuration of SPF, DKIM, and DMARC can lead to deliverability issues.
- Content Perception: Generic or unsolicited content is more likely to be marked as spam.
- List Hygiene: Poor list hygiene (inactive subscribers, high bounce rates) reduces deliverability.
Key considerations
- Engagement Improvement: Segment your audience, personalize content, and optimize send times to improve engagement rates (opens, clicks).
- Authentication Setup: Properly configure SPF, DKIM, and DMARC to verify sender identity.
- List Management: Regularly clean your email list to remove inactive subscribers and reduce bounce rates.
- IP Warm-up: Gradually warm up your IP address by slowly increasing sending volume to establish a good sender reputation.
- Dedicated IP: Consider using a dedicated IP address for sending high-volume emails to maintain control over sender reputation.
Marketer view
Email marketer from GMass details that warming up your IP address gradually before sending high volumes of emails helps to establish a positive sender reputation. This involves slowly increasing the sending volume over time and engaging with recipients to demonstrate legitimacy.
7 Jul 2023 - GMass
Marketer view
Email marketer from Reddit suggests that recruitment emails often get flagged as spam due to the content being perceived as unsolicited and generic. Personalizing emails and tailoring them to specific recipients can help improve engagement and avoid spam filters.
2 Feb 2022 - Reddit
What the experts say
4 expert opinions
Recruitment emails to higher education institutions are often marked as spam in Office 365 due to adaptive and tough spam filters. A key factor is the sender's IP address reputation. A poor IP reputation stemming from previous spam activity can lead to emails being marked as spam. Furthermore, if recipients mark the email as spam, it can receive a Spam Confidence Level (SCL) of 9, causing Office 365 to drop the mail. Proper sender authentication (SPF, DKIM, DMARC) is also crucial for improving deliverability and verifying sender identity.
Key opinions
- Adaptive Spam Filters: Office 365 employs adaptive and rigorous spam filters.
- IP Reputation: A poor IP address reputation increases the likelihood of emails being marked as spam.
- SCL:9 Marking: Emails marked as SCL:9 are often dropped by Office 365 tenants.
- Sender Authentication: Lack of proper sender authentication (SPF, DKIM, DMARC) can negatively impact deliverability.
Key considerations
- Monitor IP Reputation: Regularly check and maintain the IP address reputation used for sending recruitment emails.
- Reduce Spam Complaints: Take steps to minimize the number of recipients marking emails as spam, such as improving targeting and personalizing content.
- Implement Authentication: Ensure SPF, DKIM, and DMARC are correctly configured to verify sender identity and improve deliverability.
Expert view
Expert from Spam Resource (Laura Atkins) explains that IP address reputation is essential. If the IP address used to send recruitment emails has a poor reputation due to previous spam activity or being on blocklists, Office 365 is more likely to mark those emails as spam.
4 May 2023 - Spam Resource
Expert view
Expert from Email Geeks says that Spam filters are adaptive and always changing and O365 is one of the tougher filters.
2 Dec 2021 - Email Geeks
What the documentation says
4 technical articles
Recruitment emails to higher education institutions can be marked as spam in Office 365 due to several technical and policy-related factors. Microsoft advises following best practices for bulk email, including authenticating emails with SPF, DKIM, and DMARC, maintaining a good IP address reputation, and providing an easy way to unsubscribe. Exchange Online uses Spam Confidence Levels (SCL) to assess the likelihood of a message being spam, with high SCLs leading to filtering or rejection, influenced by content, sender reputation, and user complaints. DMARC, SPF protocols help email receivers verify that emails are authorized, preventing phishing and improving deliverability.
Key findings
- Bulk Email Best Practices: Microsoft recommends following deliverability best practices for bulk email sending.
- Spam Confidence Levels (SCL): Exchange Online uses SCL to determine the likelihood of a message being spam, influencing filtering and rejection.
- Email Authentication Protocols: SPF, DKIM, and DMARC are essential for verifying sender identity and preventing phishing.
Key considerations
- Implement Email Authentication: Properly configure SPF, DKIM, and DMARC to authenticate your email.
- Maintain IP Reputation: Ensure your sending IP addresses have a good reputation.
- Provide Unsubscribe Option: Offer an easy way for recipients to unsubscribe from your emails.
- Monitor SCL: Monitor your emails' SCL scores in Exchange Online.
Technical article
Documentation from Microsoft Learn explains that if you are sending bulk email, Microsoft advises following best practices for deliverability. This includes authenticating your email with SPF, DKIM, and DMARC; ensuring your sending IP addresses have good reputations; and providing an easy way for recipients to unsubscribe.
6 Mar 2025 - Microsoft Learn
Technical article
Documentation from RFC details technical specifications for Sender Policy Framework (SPF), explaining it allows domain owners to specify which mail servers are authorized to send email on behalf of their domain. Receivers can then verify the SPF record and reject unauthorized emails, mitigating spoofing and improving deliverability.
17 Apr 2025 - RFC
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