Webmail Returns 502 Only When People Are Actually Using It — The One Proxy Flag cPanel Forgot
A customer’s webmail threw 502 Bad Gateway every morning at nine and never during testing. Memory was fine, Cloudflare was fine, the firewall was fine. The failure was a single pooled Apache connection to cpsrvd, shared between users, that cpsrvd kept resetting. Here is the error line that proves it, the one-flag fix, and the check that confirms it.