How to escape a full email address for SMTP in the headers when the email address contains non-ascii chars

It's about sending emails with non ASCII chars in the email address.

When I use send the TO /RCPT stuff to the SMTP server I know that I need to use punycode here.

But what about the To: and From: Header. Again I know that if the User friendly part contains a non ascii char I con use the standard header encoding that I also use for the subject. But this encoding is only used for the user friendly part.

But what if the email address contains a non ascii char? How must the To header be formatted.

So how to encode "Tüst" ?

This is the encoding as far as I know.

"=?iso-8859-1?Q?T=FCst?="<tüst@domain.de>

But what with the email address.

In fact: I don't understand the RFC's. I tried hard but failed.