My school has provided us some emails with a custom domain (not @gmail.com but @myschool.smth) and we as students are only able to login via gmail, however i obviously do not want that. What can i do to prevent that? I tried logging into the email via Thunderbird but i get blocked because my administrator doesn’t allow that.
You can set up auto forwarding of emails, to add last receive mails on another client using another inbox.
If their admin is blocking the use of external email clients I wouldn’t be surprised if they’re blocking forwarding to external email addresses to as that’s a very common action taken by attackers on compromised accounts.