Maildoso mailboxes are built for B2B outreach — sending 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 part of that and 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 you get 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.
Microsoft 365 business recipients are different
Recipients on their own company domain hosted by Microsoft 365 are B2B recipients and are delivered to. For tips on landing in the inbox at Microsoft business mailboxes, see Landing in the inbox with Outlook and Microsoft recipients.
What to do
Remove consumer Microsoft addresses (and other personal webmail addresses) from your cold-email lists — they're outside the B2B use Maildoso is designed and warmed for. See What are the guidelines for sending targeted, automated B2B cold emails using Maildoso?
Use Gmail or Microsoft 365 business addresses as seed/test recipients.
If a business recipient isn't receiving your mail, that's a different situation — see Why was my email accepted but never delivered, with no bounce? and contact us with one example (sender, recipient, time, subject).