[sir]

There's no good way around that unfortunately. The proxy could build in an OAuth client for the major providers, but it's unlikely that this would be trusted by default without significant effort being put into review processes.

As the readme explains, there's nothing to stop you using the existing OAuth client details from another source (such as the many already trusted open source email clients that exist).

[emersion]

Yes. I'd argue the problem is not on the project's side, it's on the Google side (they have ridiculously high requirements for registering OAuth clients for IMAP/SMTP use, especially for a small open-source project).

[htrp]

Any good guide on this (registering oauth clients) for people who want to make the move?

[jpc0]

https://support.google.com/cloud/answer/6158849?hl=en#zippy=

There is likely a package/library for your language of choice to do a basic oauth client.