Here’s the link that gives me the answer:
[Install] the “fake sendmail for windows“. If you are not using XAMPP you can download it here: http://glob.com.au/sendmail/sendmail.zip
[Modify] the php.ini file to use it (commented out the other lines): [mail function] ; For Win32 only. ; SMTP = smtp.gmail.com ; smtp_port = 25 ; For Win32 only. ; sendmail_from = <e-mail username>@gmail.com ; For Unix only. You may supply arguments as well (default: "sendmail -t -i"). sendmail_path = "C:\xampp\sendmail\sendmail.exe -t"
(ignore the “Unix only” bit, since we actually are using sendmail)
You then have to configure the “sendmail.ini” file in the directory where sendmail was installed:
[sendmail] smtp_server=smtp.gmail.com smtp_port=25 error_logfile=error.log debug_logfile=debug.log auth_username=<username> auth_password=<password> force_sender=<e-mail username>@gmail.com
To access a Gmail account protected by 2-factor verification, you will need to create an application-specific password. (source)