Email Settings for Office 365

Here are Microsoft's recommended settings for Office 365's email service.

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
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, but unfortunately, this screen doesn't tell you which service has been enabled, or if both have been enabled. As such, it's possible for you to see, for example, IMAP settings when IMAP isn't actually turned on.

If you do not see the Sync email link, then neither IMAP nor POP has been enabled, and they either need to be enabled by you (if you're the account admin) or your IT administrator.

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 enable Authenticated SMTP.

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

Incoming Email Settings

IMAP (recommended):

User Name — full email address
Server Name — outlook.office365.com
Type — IMAP
Port — 993
Security — SSL/TLS
Password — OAuth2 (Office 365)

POP:

User Name — full email address
Server Name — outlook.office365.com
Type — POP
Port — 995
Security — SSL/TLS
Password — OAuth2 (Office 365)

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 (Office 365)

Two-Step Verification

If you are using Two-Step Verification, then you must generate an app password for Postbox.

Go 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 are using Two-Step Verification), and click on Create a new app password.

Use this password within the Postbox setup wizard.

Other Important Settings for Office 365 Accounts

Please be sure to check out these help articles: