Error details for one account

When an account can't sync, it's shown in red in Preferences > Accounts with a short explanation and two buttons. Reconnect signs in again; Error Details... opens a window with your Mailspring version, the account's server settings, and the last few hundred lines of that account's sync log. This is what to paste into a forum post (after removing anything personal).

The log files

Choose Developer > Open Mailsync Logs from the main menu (on Windows and Linux the menu is behind the button in the top right of the window, or press Alt). The folder that opens contains one mailsync-<account id>.log file per account plus the main app log. The same folder is Mailspring's data folder:

• macOS: ~/Library/Application Support/Mailspring
• Windows: %AppData%\Mailspring
• Linux: ~/.config/Mailspring

Look at the end of the file for lines marked [error] or [critical]; the IMAP or SMTP response just before them usually names the cause (for example AUTHENTICATIONFAILED, SmtpClientAuthentication is disabled, or a certificate error).

Errors in the app itself

For problems in the interface (a button that does nothing, a blank pane), open Developer > Toggle Developer Tools, switch to the Console tab, reproduce the problem, and right-click in the console to Save as... a log file.