Office 365 SMTP settings for scanners and apps

The settings

Microsoft calls this client SMTP submission (also SMTP AUTH). Type these into the device's email or SMTP settings:

SMTP server

smtp.office365.com. Don't use an IP address.

Port

587 (recommended) or 25

Encryption

TLS/STARTTLS enabled (TLS 1.2 or TLS 1.3)

Username

The mailbox's full sign-in address

Password

That mailbox's password

From address

The same mailbox, unless the sign-in account has Send As permission on another one

Before you type them in

1. Pick a licensed mailbox for the device to send from. A shared password across several devices makes it hard to change later.
2. Make sure SMTP AUTH is on for that mailbox. In the Microsoft 365 admin center: Users > Active users > select the user > Mail > Manage email apps > Authenticated SMTP.
3. Check security defaults. If they're on in Microsoft Entra ID, SMTP AUTH is already disabled.
4. Check port 587 is open from the device's network to the internet.

Sources: Microsoft Learn, How to set up a multifunction device or application to send email using Microsoft 365 or Office 365 and Enable or disable authenticated client SMTP submission (SMTP AUTH) in Exchange Online (read October 30, 2026).

Sending limits

Microsoft's limits for client SMTP submission: 10,000 recipients per day. 30 messages per minute. An app that sends invoices or statements in bulk can reach them.

When it doesn't send

The device only offers port 465

Microsoft: “If your device or application recommends or defaults to TCP port 465, it doesn't support the required versions of TLS for client SMTP submission in Microsoft 365 or Office 365.” Look for a firmware update. Microsoft lists TLS as optional for Direct Send and for an SMTP relay connector (both on port 25; see the guide).

The device can't do TLS 1.2

“If your device or application doesn't support TLS 1.2 or later, you can't use client SMTP submission with Microsoft 365 or Office 365.”

Port 25 instead of 587

Port 25 also works for client SMTP submission, but “Some network firewalls or ISPs block port 25 because that port is used by email servers to send messages.” Use 587.

It worked before and stopped

Check whether SMTP AUTH was turned off for the organization or the mailbox, whether security defaults were switched on, and whether an authentication policy blocks basic authentication for SMTP. SMTP AUTH is disabled by default for organizations created after January 2020.

The device's message tells you which: see Microsoft 365 SMTP errors (535 5.7.139, 535 5.7.3, 5.7.57), smtp.office365.com not working, and how to enable SMTP AUTH.

Sending as a different address fails

If the From address isn't the mailbox the device signs in with, that sign-in account needs Send As permission on the From mailbox.

Sources: Microsoft Learn, How to set up a multifunction device or application to send email using Microsoft 365 or Office 365 and Enable or disable authenticated client SMTP submission (SMTP AUTH) in Exchange Online (read October 30, 2026).