Hello,
I can also recommend you the Mailbird as an alternative to the Opera Mail software. Some of the benefits of this programm are first of all the fact that you can conveniently mark your important or favourite e-mails. You are also able to create your own filtered rules. In addition your profile on Mailbird can be also linked to your social media profils if you want to. You can then add contacts from your social media to your e-mail.