Checkbox on the send-test form turns on PHPMailer SMTPDebug=2 for one
send only. A Debugoutput callback captures the wire conversation;
hook is removed immediately after wp_mail returns.
AUTH credentials redacted: lines containing 'AUTH' or 16+ char base64
strings get replaced. Trace capped at 200 lines and stashed on the
session. Rendered as a collapsible <details> block on the step card.
Transport type (mail/smtp/etc., read from PHPMailer->Mailer) surfaced
in the finding detail so the technician knows whether a trace will
contain useful SMTP traffic — only the smtp transport emits any.
Steve Hanlon
9786f4e405