Manual:$wgSMTP

Details
For using a direct (authenticated) SMTP server connection, you need to fill an array with details about your connection. Set to false (the default value) to use the built-in PHP mail function.

For example:

'IDHost' is a MediaWiki-specific setting used to build the Message-ID email header (see RFC 2822, sec 3.6.4 for more information on a properly formatted Message-ID). For the remaining settings, see Mail::factory for a more complete description. (Scroll down to the  parameter.)

This setting requires PEAR's Mail package to be installed (run, and you can run "pear list" to confirm). If you get an error message stating that pear is not installed, then install  and then try again.

Examples

 * Outlook Exchange Server

Error sending mail: Unknown error in PHP's mail function Mediawiki
Put the following into LocalSettings.php, making the necessary substitutions for yourEmailAccount and yourEmailPassword:

Then install the packages required to send the mail.

After this you may get an authentication failure type error. You will need to sign into the gmail account you are using and verify that the person that just signed in is you. You only need to verify this one time. (gmail will send you an email and you just follow the instructions)

There are other possible issues listed in.