Email Settings for Office 365

Here are Microsoft's recommended settings for Office 365's email service. Please ensure that you are running Postbox 7.0.63 or higher.

Requirements

IMAP or POP MUST BE ENABLED ON THE SERVER. To check for this, ask your mail provider. Or, if you are the administrator of your account:

Log into your Microsoft email account using a web browser, and make sure you are logged out of other accounts that are not relevant to the account you are trying to set up
Click the "Gear" toolbar icon in the upper right corner, then click the "View all Outlook settings" link at the bottom
Click Mail > Sync email

If you see the Sync email link, then either IMAP or POP has been enabled. Unfortunately, this screen doesn't tell you which service has been enabled or if both have been enabled. As such, you can see, for example, IMAP settings when IMAP isn't turned on.

If you do not see the Sync email link, then IMAP and POP have yet to be enabled. You (if you're the account admin) or your IT administrator need to enable them.

Important: Authenticated SMTP must be enabled. If you can receive messages but not send them, please contact your IT Manager or ISP and submit a request to allow Authenticated SMTP.

GoDaddy Customers: Authenticated SMTP is not enabled by default! Please contact GoDaddy and request that it be enabled.

Admin Guidance

If you are the admin for this account, you can enable IMAP or POP for Office 365:

From the Microsoft 365 Admin Center, navigate to Users > Active users > [select a user] > Mail tab > Email apps > Manage email apps link
Select IMAP and/or POP, in addition to Authenticated SMTP
Click the Save Changes button at the bottom

Postbox Pre-Requisites

In a browser, ensure you are logged out of all Microsoft accounts.
Ensure that you are running Postbox 7.0.62 or higher.
Within Postbox, navigate to Options | Settings > Privacy and then select the checkbox for "Accept cookies from sites."

Incoming Email Settings

IMAP (recommended):

User Name — full email address
Server Name — outlook.office365.com
Type — IMAP
Port — 993
Security — SSL/TLS
Password — OAuth2 (Microsoft)

POP:

User Name — full email address
Server Name — outlook.office365.com
Port — 995
Security — SSL/TLS
Password — OAuth2 (Microsoft)

Outgoing Email Settings

Server Name — smtp.office365.com
Port — 587
Security — STARTTLS (if this doesn't work for you, try SSL/TLS on port 465)
Password — OAuth2 (Microsoft)

Two-Step Verification (discontinued in September 2024)

If you use Two-Step Verification, you must generate an app password for Postbox.

Navigate to the security settings for your Microsoft account at https://account.live.com/p.
Scroll down to the App passwords section (which will only appear if you use Two-Step Verification), and click Create a new app password.

Use this password within the Postbox setup wizard.

Troubleshooting

If you are receiving the following error:

"You can't sign in here with a personal account. Use your work or school account instead,"

then make the following adjustments:

1) For the server, use: imap-mail.outlook.com

2) For authentication, use "Password" and not OAuth2.

Other Important Settings for Office 365 Accounts

Please be sure to check out these help articles: