This is a real, current limitation and we would rather you read it here than discover it from a bounce.
Affected: mail sent from an agent on your own verified custom domain, to a recipient at outlook.com, hotmail.com, live.com or msn.com.
Not affected: mail from <agent>@<your-workspace>.mails.ai to anyone, including Microsoft recipients.
Not affected: custom-domain mail to Gmail, Apple, Yahoo, Fastmail, or any business domain not hosted by Microsoft.
Custom-domain sending runs on our own sending infrastructure, and the address block it sits in is currently blocked at the range level by Microsoft's consumer filter. Per-IP delisting was accepted and changed nothing, which is how we know it is a range-level decision rather than a reputation problem we can fix by behaving well.
If most of your recipients are consumers on Microsoft mail, keep those agents on your .mails.ai subdomain.
Split by agent: a [email protected] for business customers and a subdomain agent for consumer traffic is a legitimate arrangement, not a workaround.
Tell us. We route around this when we can, and knowing which customers it actually costs changes how fast that happens.
