How can I improve deliverability to Microsoft email addresses?

Microsoft has a free service, Smart Network Data Services (SNDS) that provides insight into how your IP address reputation is perceivd by the Outlook.com system.

Benefits of SNDS:

• Understand how Microsoft's filters rate your emails
• See how many users reported your email as spam
• Receive the full message with headers of any email marked as "junk" or "phishing"
• Identify potential problems with your marketing practices and content
• Improve sender reputation by removing unwanted subscribers from lists

To enroll in SNDS:

• Fill out the form here: https://postmaster.live.com/snds/addnetwork.aspx with your single IP address.
• Once you have submitted that for authorization, please let Linode Support know so that we can approve the request.

You can also peruse the below Community post which provides thorough details into other factors that contribute to deliverability issues:

https://www.linode.com/community/questions/19361/understanding-mail-deliverability-problems