Optimizely
VWO
AB Tasty
Google Analytics
Google Marketing Platform
PractiTest
Azure DevOps
Micro Focus ALM
Mu4e
Mailspring
Alpine
Mutt
Thunderbird
Claws Mail
Geary
aerc
Optimizely
Mu4eOptimizely is a lower cost entry tool for anyone looking to do website testing. While their pricing structure has changed over the years it still is a pretty cost effective solution. It is easy to get tests up and running within 5 minutes once you have code placed on your site.
I love the drag and drop features of Optimizely. It makes it very easy to make simple changes to do landing page testing for my paid search campaigns. It also frees up dev time for our web team. Also, The findings from Optimizely tests are so valuable for an end customer experience.
VWO - Use VWO to tweak, optimize & personalize your website with minimal IT help.
Mailspring - Mailspring is a mail client for Mac, Windows and Linux.
AB Tasty - AB Tasty is an all-inclusive platform for conversion rate optimization, personalization, customer activation, and testing.
Alpine - Alpine is a fast, easy to use email client that is suitable for both the inexperienced email user...
Google Analytics - Improve your website to increase conversions, improve the user experience, and make more money using Google Analytics. Measure, understand and quantify engagement on your site with customized and in-depth reports.
Mutt - Mutt is a small but very powerful text-based mail client for Unix operating systems.