Which Content-Transfer-Encoding should I use? - forms

Question

I am programmatically sending a Content-Type': 'multipart/form-data to an endpoint and my system (Ubuntu) is default on UTF-8.
My question is, which Content-Transfer-Encoding should/do I use?
Here is an example of a form part:
Content-Disposition: form-data; name="to"
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: ?
jacob#example.com
Which Content-Transfer-Encoding would be the safest to use?
Another example:
Content-Disposition: form-data; name="message"; filename="message.mime"
Content-Type: message/rfc822; charset=UTF-8
Content-Transfer-Encoding: ?
From: jacob#example.com
To: jacob#example.com
Subject: testing Coreor
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
testing Coreor

Answer 1

I have updated my code to use quoted-printable, so I now send the below.
It works, but do you see any errors, problems or optimizations?
--x.ai/coreor=---14187500275550.5525101518724114
Content-Disposition: form-data; name="to"
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: quoted-printable
jacob#example.com
--x.ai/coreor=---14187500275550.5525101518724114
Content-Disposition: form-data; name="message"; filename="message.mime"
Content-Type: message/rfc822; charset=UTF-8
Content-Transfer-Encoding: quoted-printable
X-Mailer: x.ai Coreor v1.test
From: =22Jacob=22 <jacob#example.com>
To: jacob#example.com
Subject: testing Coreor via Mailgun
Content-Type: text/plain; charset=3Dutf-8
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
testing Coreor
--x.ai/coreor=---14187500275550.5525101518724114--
I use mimelib for the quoted-printable encoding.