[solved] FRITZ!Box can not send “push” mail due to authentication error (e.g. Gmail)

I wanted to send “push” e-mail notifications about missed calls. To do this, you have to enter the corresponding e-mail data such as password and SMPT in the Fritz! During the test, I always received an authentication error despite entering the correct data. This can be caused by 2FA, among other things. The following helped me.

Create an app password
See here for Gmail
Enter the app password instead of the normal password for authentication in your Fritz!Box

I hope this has helped you. If you have any updates or additions to the problem, please let me know.