Description of problem:
Using thunderbird for IDN mail domains is not possible, because the support is complete missing.

Version-Release number of selected component (if applicable):
thunderbird-38.3.0-1.fc22.x86_64

How reproducible:
Send an mail from an IDN mail account.

Steps to Reproduce:
1. Add an new mail account for an IDN like foo
2. send an mail

Actual results:
The mails is reject by the receiver, because the header are incorrect.  

Expected results:
Send mails will work.


Additional info:
When I look in the source code of the mail, all fields, will contain the IDN and not the puny code version of the mail domain.
And also the RCPT TO:<XXX> stuff while transmit is broken.