Available from version 1.41.0 (Gerrit change 922140)
Called before sending an email, when all other checks have succeeded.
Define function:
public static function onEmailUserSendEmail( 
	MailAddress $fromAddress,
	MediaWiki\Mail\UserEmailContact $to,
	MailAddress $toAddress,
	string $subject,
	string $text,
	StatusValue $status
	MediaWiki\Permissions\Authority $from,
 ) { ... }
Attach hook: In extension.json:
	"Hooks": {
		"EmailUserSendEmail": "MediaWiki\\Extension\\MyExtension\\Hooks::onEmailUserSendEmail"
Called from: File(s): includes/mail/EmailUser.php
Interface: EmailUserSendEmailHook.php

For more information about attaching hooks, see Manual:Hooks .
For examples of extensions using this hook, see Category:EmailUserSendEmail extensions.