Notification and Messaging module for sending mails
Html mail is not reliable, buggy and some features are not supported. I've got rid of it. Mime mail is much better. Mail system and SMTP module must also be installed. 

In the settings SMTP Authentication Support SMTP server, SMTP port, User name, E-mail from address, E-mail from name must be filled, Allow to send e-mails formatted as Html could be ticked and password of your SMTP server must also be entered.

In the module Mail system in the submenu New class MimeMail_SmtpMailSystem must be constructed and filled in Site-wide default MailSystemInterface class and Mime Mail module class. In the settings Mime mail E-mail format Full HTML can be selected and Sender e-mail address need to be filled.

This configuration must work.