The Microsoft 365 SMTP settings are: server smtp.office365.com, port 587, with TLS through STARTTLS. You log in with the full email address and sign-in of a licensed mailbox. An admin must switch on SMTP AUTH for that mailbox first, because Microsoft turns it off for newer organizations.
| Setting | Value | Notes |
|---|---|---|
| SMTP server | smtp.office365.com | Use the name, not an IP address |
| Port and security | 587 with STARTTLS (TLS 1.2 or later) | Microsoft recommends 587; 465 is not supported |
| Username | Full email address of the mailbox | Must be a licensed mailbox |
| Password | OAuth (modern sign-in) recommended; mailbox password as fallback | SMTP AUTH must be on |
| IMAP (incoming) | outlook.office365.com, port 993, SSL/TLS | Same as Outlook.com |
| POP (incoming) | outlook.office365.com, port 995, SSL/TLS | Same as Outlook.com |
You can test these Microsoft 365 SMTP settings in the free SMTP Tester. The host and port are already filled in. Without a password, it checks that the server answers and the TLS lock works. If you enter the mailbox login, it can send one test message.
What do SMTP, SMTP AUTH and STARTTLS mean?
SMTP is the system that sends email. SMTP AUTH means your app proves who it is before Microsoft accepts the message. Microsoft calls this "SMTP client submission". It is the right choice for a WordPress site, a contact form, a printer or a scanner that sends from one mailbox.
A port is a door number on the server. On port 587, the app connects and then sends STARTTLS, a command that turns on TLS encryption. TLS is a lock that hides your login and your mail on the way. Microsoft says the device must support TLS 1.2 or later.
What do you need before you start?
Microsoft lists a few things you need before SMTP AUTH works:
- A licensed Microsoft 365 mailbox to send from.
- Port 587 open on your network or web host.
- SMTP AUTH switched on for that mailbox. Microsoft disables it for organizations created after January 2020.
- Security defaults turned off. Microsoft says SMTP AUTH does not work while security defaults are on.
An admin can turn on SMTP AUTH for one mailbox in the Microsoft 365 admin center:
- Go to Users, then Active users, and pick the user.
- Open the Mail tab and select Manage email apps.
- Tick Authenticated SMTP.
- Select Save changes.
Microsoft also recommends modern sign-in (OAuth) over a plain password. With OAuth, the app opens a Microsoft sign-in page and gets a token, a kind of pass, instead of your password. Microsoft has said it will remove plain password sign-in (Basic authentication) for SMTP AUTH. So pick an app or plugin that supports OAuth now.
How do you use Microsoft 365 SMTP settings in WordPress?
Look first for a plugin mailer that signs in with a Microsoft account. It handles OAuth for you, so you never type the password into WordPress. If you must use a generic option, such as "Other SMTP" in WP Mail SMTP, enter:
- SMTP Host:
smtp.office365.com - Encryption: TLS (STARTTLS)
- SMTP Port: 587
- Authentication: on
- SMTP Username: the full address of the mailbox
- SMTP Password: the mailbox password
- From Email: the same address as the username
Keep the From address equal to the login. Microsoft says you can send as another address only if the login account has Send As permission for it. For a personal Hotmail or Outlook.com address, use the Outlook.com SMTP settings instead.
How do you add the mailbox to an email app or phone?
Modern apps such as Outlook, Apple Mail and Thunderbird can sign in to Microsoft 365 with OAuth. Pick "Microsoft" or "Exchange" when you add the account, then sign in on the Microsoft page. If an app needs manual servers, use IMAP outlook.office365.com on port 993 and the SMTP values above.
Does Microsoft 365 limit SMTP sending?
Yes. Microsoft's guide to SMTP client submission lists a limit of 10,000 recipients per day and 30 messages per minute. Microsoft also says this method does not support bulk mail or newsletters. Those limits suit site alerts and forms. For mass mail, use a mailing service.
What do common Microsoft 365 SMTP errors mean?
- 535 5.7.3 Authentication unsuccessful: Microsoft refused the login. Check that SMTP AUTH is on for the mailbox and that the password is right. Microsoft's troubleshooting page also points to security defaults, multi-factor sign-in and policies that block older sign-in methods.
- 5.7.57 Client not authenticated to send mail: the app did not log in, or SMTP AUTH is off. Turn on authentication in the app.
- 5.7.60 Client does not have permissions to send as this sender: the From address differs from the login. Use the same address or give Send As permission.
- 550 5.1.8 Bad outbound sender: Microsoft blocked the mailbox for spam. An admin must remove it from the Restricted Users list.
- Connection timed out: your host blocks port 587. Ask your host to open it.
Why does mail from your domain land in spam?
Your Microsoft 365 mailbox uses your own domain, so your domain's DNS must vouch for Microsoft. You do that with SPF, DKIM and DMARC records. They tell receiving servers which services may send mail for your domain. Learn what an SPF record is, then check your domain with the free DNS & Email Checker.
If you only just moved the domain, also check where it points. The guide on how to point a domain to hosting explains the DNS basics.
The Microsoft 365 SMTP settings work once SMTP AUTH is on and the app signs in properly. Check the connection in the SMTP Tester, then send a real test from your site. You can compare other providers in the list of SMTP settings for other email providers.
Frequently asked questions
Why does Microsoft 365 say SMTP AUTH is off?
Microsoft switches SMTP AUTH off for organizations created after January 2020, and security defaults also block it. An admin can turn on Authenticated SMTP for one mailbox in the admin center. Turn it on only for the mailboxes that need it.
Can I use port 465 with Microsoft 365?
No. Microsoft says devices that only use port 465 do not support SMTP client submission. Use port 587 with STARTTLS. Microsoft also allows port 25, but most web hosts block it.
Can a shared mailbox send through SMTP?
SMTP client submission needs a licensed mailbox to log in with. A licensed account can send as another address only if it has Send As permission. Without it, Microsoft returns error 5.7.60.
