mail-tester.com : Free online service that allows you to test your emails for Spam, Malformed Content and Mail Server Configuration problems
MailHog : MailHog is an email testing tool for developers:
Configure your application to use MailHog for SMTP delivery
View messages in the web UI, or retrieve ...
Tutanota : Tutanota is an open-source end-to-end encrypted email software and freemium hosted secure email service based on this software
Mautic : Mautic is marketing automation software (email, social & more). Social Media Marketing, Contact Management, Email Marketing, Forms, Campaigns, Reports
Greasemonkey : Greasemonkey is a Firefox extension that allows you to customize the way webpages look and function.
Firefox addon to simplify the use of temporary e-mail addresses in order to protect your real address from spam.