Add tools for email testing

[vveliev-tc]

Not sure where to add following tools for dev environment that help speeding up email testing
https://github.com/antespi/docker-imap-devel
https://github.com/sj26/mailcatcher
https://github.com/mmower/mailtrap
https://github.com/greenmail-mail-test/greenmail

[poliarush]

I think it should go per programming language usage. A few should be put to ruby and other to java.

[vveliev-tc]

But it's a general tool that is not depending on your code. More like fake email service