How to change the outgoing mail port in Outlook from 465 to 587

If Outlook receives emails but you can’t send them, check the outgoing mail server (SMTP) port. For security reasons, our SMTP server no longer accepts connections on port 465. Change it to port 587 with STARTTLS security.

Do not change the server name, username, password, or incoming mail settings.

Classic Outlook for Windows

In Outlook, open File → Account Settings → Server Settings.
Select Outgoing mail.
In Port, change the value from 465 to 587.
As the encryption method, select STARTTLS.
Check that outgoing server authentication is enabled. Outlook should use the same login details as for incoming mail.
Save the settings using Next → Done.
Send yourself a test email.

If you don’t see the Server Settings option in your Outlook, use this procedure:

In Windows, open Control Panel and search for Mail (Microsoft Outlook).
Click Email Accounts.
Select your account and click Change → More Settings.
On the Advanced tab, change Outgoing mail server (SMTP) from 465 to 587.
For the encrypted outgoing mail connection, select STARTTLS.
Confirm the settings and run the account test.

New Outlook for Windows

Open Settings → Accounts → Your accounts.
For your email account, choose Manage.
If the Repair option is available, open it and display the advanced or manual account settings.
For the outgoing SMTP server, set port 587 and security STARTTLS.
Save the change and send yourself a test email.

Some versions of the new Outlook do not allow you to edit the server settings for an existing account. In that case, remove the account and add it again manually. When adding it, show advanced options and set port 587 and security STARTTLS for outgoing mail.