How do subdomains affect root domain reputation and how can I fix Microsoft O365 Outlook SCL:5 spam filtering issues?

Email marketer from GMass advises to only send emails to recipients who have opted-in and have a genuine interest in receiving your messages. Regularly clean your email list to remove inactive or invalid addresses to reduce bounce rates and improve your sender reputation.

Email marketer from Litmus shares that ensuring proper email authentication using SPF, DKIM, and DMARC is crucial for improving deliverability and preventing spoofing. DMARC policies help instruct receiving servers on how to handle emails that fail authentication, preventing malicious use of your domain.

Email marketer from SparkPost's blog shares that subdomains are valuable for segmenting email streams. Using a dedicated subdomain for transactional emails, marketing emails, and internal communications is best practice. This helps isolate reputation; for instance, if your marketing campaigns encounter deliverability issues, your transactional emails will remain unaffected.

Email marketer from Stack Overflow suggests that if emails are consistently marked as SCL 5, you should analyze email content for spam triggers, check the sending IP's reputation, and make sure recipients add the sender to their safe sender list. Contacting Microsoft support and requesting a reputation review is also advisable.

Email marketer from Reddit suggests that an SCL of 5 often means your sending IP or domain has a poor reputation with Microsoft. They recommend checking if you're on any blacklists, ensuring your domain is properly authenticated, and contacting Microsoft support for assistance. They also advise reviewing your sending practices and content for anything that might trigger spam filters.

Email marketer from SendGrid recommends warming up new IPs and domains gradually to establish a sending reputation. Start with small volumes to engaged users and slowly increase sending volume over time. Monitor deliverability and adjust sending practices based on results to ensure a good reputation with ISPs.

Email marketer from Postmark explains that domain reputation is built over time based on sender behavior and recipient engagement. Monitor bounce rates, spam complaints, and engagement metrics, and address any issues promptly to maintain a positive reputation and ensure good deliverability.

Email marketer from Microsoft Learn explains that while each subdomain initially builds its own reputation, negative actions on a subdomain (like spam complaints) can eventually affect the reputation of the root domain, leading to deliverability issues for all subdomains. Conversely, positive actions like high engagement can improve the overall reputation.

Email marketer from Mailjet shares that using subdomains allows you to isolate your sending reputation. If one subdomain is sending problematic emails, it will impact the reputation of that subdomain, not necessarily your main domain. However, consistently poor practices across multiple subdomains can reflect negatively on the overall brand reputation.

Email marketer from MailerQ shares that in regards to emails landing in the Junk/Spam folder of Hotmail, Outlook and Office 365, the Spam Confidence Level (SCL) checker is Microsoft's measurement to rate a message between -1 and 9. With 5 or higher normally meaning it ends up in the spam folder.

Marketer from Email Geeks advises against using warm-up services, calling them snake oil and warning they can further damage domain reputation.

Expert from Email Geeks states that subdomain reputation does impact root domain reputation, but the extent to which it can repair a domain's reputation is unclear.

Expert from Spam Resource shares that when debugging deliverability issues into Microsoft, understand an SCL score of 5 and above indicates messages are highly likely to be filtered as spam. Investigate authentication, content, and sending practices when encountering this score.

Expert from Word to the Wise explains that subdomains do affect the reputation of the root domain. Problems on a subdomain will impact the main domain. Proper authentication, list hygiene, and engagement are important for both.

Expert from Email Geeks explains that improving domain reputation with Microsoft when mail is going to spam (SCL:5) is difficult through 1:1 emails. They recommend recipients regularly move mail from the spam folder to the inbox. They also advise opening a ticket with Microsoft, clearly stating the issue is with domain reputation and requesting a reset. Persistence, using the words 'escalation' and 'reputation reset' is key, even when receiving boilerplate responses.

Documentation from Microsoft Learn explains that an SCL (Spam Confidence Level) of 5 indicates that a message is considered highly suspicious and is likely spam. The higher the SCL, the more likely it is that the message will be filtered as spam by Exchange Online Protection (EOP) or Outlook.

Documentation from Microsoft Learn explains that to improve sender reputation, ensure your sending domain is authenticated with SPF, DKIM, and DMARC. Maintain low spam complaint rates, avoid sending to invalid email addresses, and ensure your content is not spammy. Requesting delisting through the delisting portal if blocked is also recommended.

Documentation from Microsoft states that if your IP address or domain has been blocked by Microsoft's filtering systems, you can use the delist portal to request removal. Provide all necessary information accurately and follow any instructions provided by Microsoft to increase the chances of a successful delisting.

Documentation from RFC Editor explains that a properly configured SPF record lists all authorized sending sources for your domain. This helps receiving mail servers verify that the email is legitimately sent from your domain and reduces the likelihood of being flagged as spam. Check and validate your SPF records to ensure accuracy.