Microsoft mailboxes — including Outlook.com, Hotmail, Live, and Microsoft 365 (business) addresses — filter incoming mail strictly and build sender reputation slowly. It's common to see good placement at Gmail while Microsoft inboxes are still routing your messages to spam, especially from newer domains. This guide explains why that happens and what you can do to improve it.
Why Microsoft inboxes can be tougher
Microsoft relies heavily on the sending reputation of your domain and IP, plus how recipients engage with your messages. New domains start with no reputation, so Microsoft tends to be cautious until you've built up a consistent, healthy sending history. A domain that lands fine at Gmail can still need more time to earn trust at Microsoft.
What's already handled for you
Email authentication (SPF, DKIM, and DMARC) is set up and managed automatically for your Maildoso domains, so you don't need to add these records yourself.
If a domain shows a warning such as missing MX or authentication issues, that's worth resolving first — reach out and we can check it for you.
Steps to improve placement at Microsoft
Keep warmup running on every mailbox, and let new mailboxes warm up for a few weeks before you rely on them for real sending.
Ramp your sending volume up gradually. Sudden spikes from a new domain are the fastest way to trigger filtering.
Send consistently rather than in bursts. Mailboxes that sit idle and then send a large batch tend to perform worse than ones that send a steady, modest daily volume.
Only email valid, engaged recipients. High bounce rates and spam complaints damage your reputation at Microsoft quickly, so verify your lists and remove invalid or unresponsive addresses.
Keep your message content natural and personal. Avoid spammy phrasing, excessive links, large images, and link shorteners, which Microsoft's filters weigh heavily.
Encourage replies. Genuine back-and-forth engagement is one of the strongest positive signals you can build.
Run inbox placement tests that include Outlook/Microsoft seed addresses so you can track your progress over time rather than guessing.
If only some of your domains are affected
If a couple of domains land well and others don't, the difference is usually reputation and activity: the well-performing domains have been sending consistently and warming up longer. Bringing your quieter domains up to the same steady warmup and sending pattern usually closes the gap over time.
Still landing in spam at Microsoft?
Microsoft placement can take longer to recover than other providers, so give changes a couple of weeks to take effect. If specific domains continue to land in spam at Outlook or Microsoft 365 after that, contact us with the affected domains and we'll review your specific case.