pfsense with outlook mail and dual WAN

[SoerenKaiser99]

Hi together,

I have dual WAN, Starlink as the main provider and DSL mainly as a backup and a voip line that does not run with Starlink because it is carrier-based.

The setup is generally going well. I only have spamhouse and guest restrictions. The rest is open with any any in the home-net. Lan has some rules regarding phone-net and DNS for Adguard (runs on synology docker - 192.168.2.165) and also loadbalancing. Sticky conn. are activated.

3 mail accounts are configured in Outlook (vers.16,54 Outlook 365) 2x google which work without any problems and a hosting provider called webgo24. This always causes problems.
I have configured the account correctly and if I connect to the WLAN on the Mac, it also syncs the mail.
After a few minutes, the account is offline. New mail arrives and is sent every 10-15 minutes. The account is then offline again and emails cannot be sent. If I connect again in between, it works again for one to two minutes.

In every other WLAN it works permanently, which eliminates an outlook configuration error. Does anyone have an idea where the problem could lie?

Ports used are 993 & 587 for the webgo acc.
Home is the net which is linked to the WLAN

Attached pictures of the rule-config. Sorry If i forgot something - im new to this topic

Thank you in advance!
Greeting Soeren