* Ensure that the provided username actually contains a domain
* Update README.md to be consistent with addmailuser script
* Add a test to check if the username includes the domain
* Add some checks for user name matching in mail user scripts
* Fix user matching problems in mail user scripts
** fix matching problems at several places:
"delmailuser a@example.com" deletes also user "aa@example.com"
"delmailuser a@sub.example.com" deletes also user "a@sub-example.com"
** similar problems when inserting
** refactor and clean up
* Wrote functional tests for desired behavior.
Redoing the pull request, starting from current master.
The tests now fail where expected.
* Updated commands to handle missing files better.
The functional tests now pass.