Default email sender is not working

[alansemenov]

If defaultFromEmail is set in the XP mail configuration, it should be used in outgoing emails when it's not explicitly specified.

Examples (assume that defaultFromEmail is set to noreply@enonic.com):

1. If an email is sent with Some Name<email@domain.com> as a sender, use that as is.
2. If an email is sent with email@domain.com as a sender, use that as is.
3. If an email is sent with Some Name<> as a sender, substitute value from defaultFromEmail so that it's sent from Some Name<noreply@enonic.com>.
4. If an email is sent with <> as a sender or sender not specified, use value from defaultFromEmail so that it's sent from noreply@enonic.com.

Throw an error if the value from defaultFromEmail is required (like in cases 3 and 4 above) but not configured.