Unable to use contact form in CeeVee

I've correctly set up the email plugin and tried all available options (smtp, sendmail, php mail), but when I click submit, my site hangs and eventually I'll get a gateway timeout error from Nginx. I've installed sendmail, though I have no idea if that's actually needed for the other two options to function. I don't know where to start to debug. Any ideas?

Ok, it get's even stranger. If I fill out the form, a mail is sent to the email address that is provided by the one filling it out, instead of the email address that I configured in the email plugin. The site still hangs after I click submit.

Ok, I found out that there is a bug in CeeVee where the from address instead of the to address is used from the email plugin. Only the 503 error remains.

https://github.com/getgrav/grav-plugin-email/issues

Looking. Thanks