From the pictures and updated information, Gmail is forwarding the email inline. Vanilla Gmail appears to only support forwarding emails inline. When emails are forwarded "inline", only a small amount of information from the original email is preserved. As shown in the pictures, the headers
To are extracted from the original message and rendered in text form in the inline-forwarded email.
The technique your helpdesk system uses for forwarding emails replaces the
From with helpdesk's own email address. This is necessary because otherwise Gmail's SPF policies would cause it to reject the mail or immediately mark it as Spam/Junk. Since your helpdesk system puts the original sender's email in
Reply-To, you can still reply to those messages to reply to the original sender. However, if you forward the email inline, Gmail's inline-mail-header-formatter will not copy the
Reply-To header because it just doesn't. That is, Gmail is keeping the
From; it is your own internal system that is losing the
From before the message gets to Gmail. And Gmail does not preserve
Now, it is possible to forward emails as MIME attachments in Gmail. If you did this, the receiver of the forwarded email would be able to see the original
Reply-To header of the attached email. However, this is an involved and impractical process because Gmail's web interface is not able to do the work for you. I would suggest using Gmail's feedback feature to request support for forwarding emails as MIME attachments (as this is a standard feature in desktop mail clients). Another option is to set up a desktop email client (but that solution is outside the scope of "WebApps”, hmm…) with Gmail since it will not have this limitation.