Mail app is not showing whole messages

Hello,
I’m new to this forum. I signed up here because I have a problem with the mail app of Nextcloud. When I open a mail in the mail app it only shows me a portion of the message (see picture):

Has anyone an idea how to fix this? I’m running Nextcloud with the fpm-alpine image in a docker container.

The solution of the problem is the same as in this thread:
https://help.nextcloud.com/t/nextcloud-login-issue-google-chrome/65958

I use a reverse procy and was having the same issue in Mail on NextCloud v.7 (28.0.1). Only a portion of my email messages were visible. I followed the advice in this thread and although the situation is vastly improved, I am still seeing some partial text at the bottom of the mail window. As I’m unable to scroll down in the email window, or to open the mail in a separate window, I cannot access the missing part of the email message.