Which Microsoft account do you have?
| Account | SMTP with a password? |
|---|---|
| Microsoft 365 / Exchange Online (work or school, your own domain) | Yes, if your admin allows SMTP AUTH. Microsoft turns it off by default at the end of December 2026. |
| Outlook.com, Hotmail, Live, MSN (personal) | No. Microsoft removed password (Basic) sign-in for these accounts on September 16, 2024. Only OAuth works. |
FormSMTP signs in to SMTP with a username and password, so it can’t use a personal Outlook.com, Hotmail or Live address. If that’s your only mailbox, connect a sending service such as Brevo, Amazon SES or Resend, or use Gmail.
1Make sure SMTP AUTH is allowed (Microsoft 365)
Microsoft 365 controls SMTP sign-in at two levels. Your admin can check both:
- The organization: if security defaults are on in Microsoft Entra ID, SMTP AUTH is disabled for everyone. Conditional Access policies that block legacy authentication have the same effect.
- The mailbox: in the Microsoft 365 admin center, open the user, then Mail → Manage email apps, and tick Authenticated SMTP.
Microsoft recommends enabling it only for the mailboxes that need it. A dedicated address such as website@yourdomain.com is a good fit.
2Create the FormSMTP project
Sign up free, add a project and pick Outlook / Microsoft 365 as the provider so the host and port fill in.
3Enter the settings
| Provider | Outlook / Microsoft 365 |
| Host | smtp.office365.com |
| Port | 587 with SSL off (STARTTLS) |
| Username | The mailbox’s full email address |
| Password | The mailbox password |
| From email | The same address, or one the mailbox has Send As permission for |
Click Test connection, then add your form. See the HTML contact form guide, or compare every provider on the SMTP settings page.
The 2026 deadline
Microsoft is retiring password (Basic) authentication for SMTP AUTH in Exchange Online. After postponing the original March–April 2026 shutdown, its current plan is:
- End of December 2026: SMTP AUTH with a password is disabled by default in existing tenants. Admins can still turn it back on.
- Tenants created from 2027: password SMTP AUTH isn’t available; only OAuth is.
- Second half of 2027: Microsoft will announce the final removal date.
If you’re setting up something new, a sending service with your own domain verified (SES, Brevo, Resend, Mailgun, SendGrid) won’t be affected, and your email still comes from your address.
Common errors
- 535 5.7.139 Authentication unsuccessful, SmtpClientAuthentication is disabled for the Tenant: SMTP AUTH is off for your organization. Your admin can enable it, or turn off security defaults.
- 535 5.7.139 Authentication unsuccessful, the user credentials were incorrect: wrong password, or a policy (MFA, Conditional Access) blocks password sign-in for this mailbox.
- 550 5.7.60 Client does not have permissions to send as this sender: the From address isn’t the mailbox you signed in with. Use the same address, or grant Send As.
- Authentication fails for an @outlook.com or @hotmail.com address: expected. Personal Microsoft accounts no longer accept passwords over SMTP.
FAQ
Can I use my Outlook.com or Hotmail address?
No. Since September 16, 2024, personal Microsoft accounts only accept OAuth for SMTP, and FormSMTP signs in with a password. Use a sending service with your own domain, or Gmail with an App Password.
Will Microsoft 365 SMTP stop working?
Password SMTP AUTH is disabled by default at the end of December 2026 for existing tenants, though admins can re-enable it until Microsoft announces a final removal date (expected in the second half of 2027).
Should I use port 587 or 465?
Use 587 with STARTTLS (SSL off in FormSMTP). That’s the port Microsoft documents for SMTP AUTH client submission.