save lengthy call into a variable
don't use split for addresses, use parser
turn blacklist into a hash with reasons

* to make log clearer about why we blacklist recipients
* make sure we use case insensitive email comparision
explain in logs why email is in blacklist
Make messages more verbose and actionable
Remove the trailing newline from the msgid before logging using it
Refactor RemoveInappropriateRecipients to use a callback interface

This allows other subclasses to add their own particular cases for why
an address should be skipped, by overriding
RemoveInappropriateRecipients to call an additional RecipientFilter.
Use RecipientFilter to provide a log message when NotifyActor kicks in
Rewrite test to use terser RT::Test::Email mail_ok method
Ensure that no warnings are generated during the tests
Add a test to ensure that RTAddressRegexps are always squelched, even when CC'd
Merge branch '4.2/sendmail-action-logs'