reset password mail: One with from and one without from

Greetings community,

I have followed phenomenon with the reset password function:

Has the mail receiver a microsoft exchange server, the mail looks like correct:
---------------------------------------------------
From: support@domain.com
mailbody ---------------------------------------
Dear Testuser,
your new password is: XYZ
--------------------------------------------------

If send the application the same mail to a normal IMAP account, the information are worng:---------------------------------------------------
From: <this field is empty>
mailbody ---------------------------------------
=?UTF-8?B?b3J0cy4=?=
Content-Type: text/plain; charset=UTF-8; format=flowed
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
From: support@domain.com

Dear Testuser,
your new password is: XYZ
--------------------------------------------------

In both cases are the same application.
What could be the reason here?
Thank you very much for a hint!
Michael