I want to customize K-9Mail

I need to customize this K-9 mail.(Only for Android)

If I change the package name.
The Mail function that interacts with server sides(like google, apple, yahoo …) will not work.
is that right?
How can I customize K-9mail?


You need to register your own OAuth 2.0 client IDs with those providers. Currently those are configured via build.gradle.kts.

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Thanks for your reply.

This K9 is using AppAuth-Android.
(GitHub - openid/AppAuth-Android: Android client SDK for communicating with OAuth 2.0 and OpenID Connect providers.)

How can I register my own OAuth 2.0 client IDs? where?

I wonder this k9 also has it’s own backend side?
So If I want to customize, should I build my own backend too?


I registered Google’s OAuth client id for my new debug domain as Android
And update the OAuth Client ID from gradle file.

But error occurs.
Access blocked: request is invalid.