Microsoft mailboxes filter incoming mail strictly and build sender reputation slowly. It's common to see good placement at Gmail while Microsoft inboxes still route your messages to spam, especially from newer domains. This guide explains which Microsoft recipients Maildoso delivers to, why Microsoft can be tougher, and what you can do about it.
Personal Outlook.com, Hotmail and Live addresses aren't delivered
Maildoso mailboxes are built for B2B outreach to business addresses on company domains. Mail addressed to personal Microsoft consumer accounts (outlook.com, hotmail.com, live.com and other consumer Outlook domains) is not delivered from Maildoso mailboxes. This is a platform policy, not a reputation problem with your domain. What you'll see:
your sending tool shows the message as sent (the SMTP server accepts it), but the recipient never receives it and there's no bounce;
the same mailbox delivers normally to Gmail, Google Workspace and Microsoft 365 business addresses;
a test sent to your own personal Outlook.com/Hotmail address never arrives — so don't use one as a seed address for placement tests.
Other personal or consumer webmail (Gmail, Yahoo, qq.com, 163.com and similar) is also outside Maildoso's B2B focus: personal Gmail addresses may technically receive mail but aren't recommended targets, and sending to consumer addresses can lead to suspension under our terms. Remove them from your cold-email lists and use Gmail/Google Workspace or Microsoft 365 business addresses as seed recipients. See B2B cold email best practices and sending guidelines.
Microsoft 365 business recipients: why they can be tougher
Recipients on their own company domain hosted by Microsoft 365 are B2B recipients and are delivered to. Microsoft relies heavily on the sending reputation of your domain plus how recipients engage with your messages. New domains start with no reputation, so Microsoft is cautious until you've built a consistent, healthy sending history — a domain that lands fine at Gmail can need more time to earn trust at Microsoft.
Email authentication (SPF, DKIM and DMARC) is set up and managed automatically for your Maildoso domains. If a domain shows a warning such as missing MX, resolve that first — contact us and we'll check it.
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 — see How warmup works and how to start it.
Send consistently rather than in bursts, and never spike volume from a new domain. Mailboxes that sit idle and then send a large batch perform worse than ones sending a steady, modest daily volume.
Only email valid, engaged recipients — high bounce rates and spam complaints damage your reputation at Microsoft quickly.
Keep 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 is one of the strongest positive signals.
Run inbox placement tests that include Microsoft 365 seed addresses so you can track progress rather than guessing.
Track your Microsoft reputation in the dashboard
Each mailbox shows a Microsoft Score on the Email accounts page and in its details panel, so you can watch it improve as warmup and steady sending build reputation. A new mailbox often reads low at first — that's expected. See Understanding your mailbox reputation scores.
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 the 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. If specific domains keep landing in spam at Microsoft 365 after that, contact us with the affected domains. If a business recipient isn't receiving your mail at all, see Why was my email accepted but never delivered, with no bounce? and send us one example (sender, recipient, time, subject).