GHSA-R553-M4FV-5V97 Mailpit: SMTP DATA line reader buffers over-limit input before size enforcement

Summary Mailpit's SMTP DATA reader enforces the configured MaxMessageSize only after bufio.Reader.ReadBytes'\n' has already buffered a complete DATA line. A remote unauthenticated SMTP client can send one line larger than the configured message-size cap and force memory allocation before Mailpit...