GMail requires using a TLS-encrypted SMTP connection which wasn't supported prior to the version 2.2. Please follow these steps to setup GMail on 2.2 or later:
1. Install the Perl module named 'Net::SMTP::TLS'
2. Edit XFileConfig.pm in the following way:
smtp_server => 'smtp.gmail.com',
smtp_user => '<your_login>@gmail.com',
smtp_pass => '<your_password>',
3. Find the field named 'smtp_auth' and set it to 'tls'.