Timezone in Date: header of tickets created by email

Tickets created by email have GMT instead of local timezone in the Date: header:

Wed Jun 03 09:17:10 2020 {{user}} - Ticket created
From: {{user}}
Subject: Test
Date: Tue, 2 Jun 2020 23:17:08 +0000
To: {{address}}

Tickets created via the web interface have the local timezone in that header.

I would like to display the local timezone in all cases.

The timezone on the mailserver is correct, and $Timezone in RT_SiteConfig.pm is correct

Does anyone know where to configure this?

My guess would be that the email server sending the email sets that header