Html emails are shown in a tiny preview iframe even if there is a lot more space that the iframe could use

[xX-MrN0b0dy-Xx]

Steps to reproduce

1. Deploy a new Nextcloud instance from scratch and perform preliminary configuration
2. Install Mail app, it will install "Mail 5.10.3" (latest version)
3. Open the app and configure a client
4. Open an html mail from the inbox or any folder

Expected behavior

Correctly show the mail in an iframe utilizing entire available space

Actual behavior

Only a small portion of vertical available space is used for the iframe

Mail app version

5.10.3

Nextcloud version

33.0.5

Mailserver or service

Mailcow

Operating system

Linux 6.18.29+rpt-rpi-2712 aarch64

PHP engine version

8.4.22

Nextcloud memory caching

No response

Web server

Apache

Database

MariaDB 11.8.8

Additional info

I found out that this happens only on new instances configured from scratch with Nextcloud version 33.0.5 and Mail 5.10.3. I have another instance that was running "Mail 5.9.2" and after updating it, the problem isn't showing up (same client, same mail used for testing).

So, I think this has something to do with preliminary config files created installing latest mail version, that fixed #13028 .

Moreover, I think that something like this probably already happened in the past, see #3696 .

Browsers utilized:

• Safari 26.5 (21624.2.5.11.4) MacOS 26.5.1
• Firefox 152.0.1 (aarch64) MacOS 26.5.1
• Firefox 152.0.1 x86 Fedora KDE 44 rpm version