Mail addresses encoded according to RFC2047 are not displayed correctly

[weissreto]

Describe the bug
If I send a mail to a mail address with special uniccode characters like:
Hans Müster [email protected]
then the mail address is shown in its encoded form:
=?UTF-8?Q?Hans_M=C3=BCster?= [email protected]

To Reproduce
Steps to reproduce the behavior:

1. Send a mail with non US ASCII characters in on of its mail addresses
2. View the mail in the Email Message View

Expected behavior
Instead of displaying the mail address:
=?UTF-8?Q?Hans_M=C3=BCster?= [email protected]
the correct mail address should be displayed
=?UTF-8?Q?Hans_M=C3=BCster?= [email protected]

Screenshots

Desktop (please complete the following information):

• OS: Windows
• Eclipse: Photon 4.8
• Java: 8

Additional context
Add any other context about the problem here.