Overview
If the browser-based sign-in window closes unexpectedly, times out, or fails to return you to Mailbird Next, the problem is usually related to the OAuth2 authorization flow rather than your password itself.
This article covers cases where the user cancels the flow, the token exchange fails, or the connection drops during sign-in.
Try these fixes in order
Start the sign-in again from the beginning. Many OAuth2 issues are temporary and are resolved by retrying the authorization flow.
Complete the sign-in in your default browser. If Mailbird opens an external browser window, avoid switching accounts midway through the process.
Use the same account all the way through. Signing in with a different account than the one you started with can cause the flow to fail.
Make sure your internet connection is stable. OAuth2 needs a working connection to your provider during every step of the process.
Temporarily disable VPN, proxy, or browser privacy tools if they interfere with the login redirect.
Common OAuth2 failure scenarios
The sign-in was cancelled or timed out
Restart the sign-in and complete it without closing the browser window. If your provider asks for confirmation in multiple steps, make sure every step is completed before returning to Mailbird.
The token could not be retrieved
This usually means the provider accepted the login, but Mailbird did not receive the final authorization token correctly.
Retry the sign-in
Sign out of the provider in the browser and sign in again
Try again after reducing browser session conflicts, such as multiple signed-in accounts
The connection failed during OAuth2
Check your network, disable VPN or proxy temporarily, and try again. Temporary provider outages can also interrupt the flow.
Provider-specific notes
Gmail: Use the Gmail provider flow and follow the browser sign-in to completion.
Outlook or Microsoft 365: Use the Outlook or Microsoft provider flow rather than manual password-based setup when OAuth2 is offered.
Still need help?
If the issue continues, contact support and include the exact message shown by Mailbird, your email provider, and whether the browser window closed, timed out, or displayed an error page.