Unable with using manual mode to server login

[GentleRV]

Steps to reproduce

1.Install de mail app
2.select manual mode
3.Input the needed information to make connection with the IMap and SMTP server

Expected behavior

1. confirmation from the Imap server thet connection and transfer of the SSL key is done and login is possible
2. After that login to the SMTP server with given credentials

Actual behavior

I see in the GUI from the Mercury server that a request is made to login but it fails wit making a connection, after this the SMTP part is not executed.
Error Imap connection failed is returned

Mail app version

late4st

Nextcloud version

34.0.1

Mailserver or service

Mercury Mailserver (David Harris)

Operating system

Ubuntu

PHP engine version

PHP 8.3

Nextcloud memory caching

none

Web server

Nginx

Database

MariaDB

Additional info

Any help from my side to get the mail app working is possible