Microsoft 365 SMTP relay uses the tenant MX endpoint on port 25 and authenticates through an inbound connector, using a TLS certificate whose Subject/SAN matches an accepted domain or a static, unshared public IP. It needs no licensed mailbox and can relay to external recipients.
Checked 2026-10-02
- Vendor
- Microsoft
- Product
- Exchange Online
- Subsystem
- SMTP relay connector
- Deployment
- multi-tenant
- Region
- not restricted
- Release range
- current as of 2026-10-02
- Checked
- 2026-10-02
Sources
- How to set up a multifunction device or application to send email using Microsoft 365 or Office 365 — Microsoft · tier 2 current vendor documentation · SMTP relay: Configure a connector to relay email ... (requirements and settings tables)
Cite this note
APA
WarmTransfer. (2026, October 2). Troubleshooting Unity Connection voicemail-to-email and notifications: source note unity-connection-notification-troubleshooting-m365-relay-conn. WarmTransfer. https://warmtransfer.net/knowledge/claims/unity-connection-notification-troubleshooting-m365-relay-conn
BibTeX
@misc{warmtransfer-claim-unity-connection-notification-troubleshooting-m365-relay-conn,
title = {Troubleshooting Unity Connection voicemail-to-email and notifications: source note unity-connection-notification-troubleshooting-m365-relay-conn},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/unity-connection-notification-troubleshooting-m365-relay-conn},
note = {Source note unity-connection-notification-troubleshooting-m365-relay-conn, checked 2026-10-02}
}