Thanks to @kevinbytnar for the Canon Maxify MB2755 report

[msgwing]

Thanks to @kevinbytnar for reporting that on the Canon Maxify MB2755, disabling certificate verification ("Nie weryfikuj certyfikat" / "Don't verify certificate") was necessary to get scan-to-email sending over SMTP working. This case is documented in docs/PRINTERS.md, along with the technical explanation (this model's firmware root store predates and does not trust the ISRG Root X1 chain).

[msgwing]

Update, thanks to @kevinbytnar retesting this today: certificate verification also needs to stay off on port 587, not just 465 — an earlier version of the docs said 587 didn't need the workaround, which turned out to only be true for the certificate chain the server happened to be presenting at the time.

Checked this independently against the openssl s_client -connect mx.msgwing.com:587 -starttls smtp output: the chain is currently fully ECDSA (leaf → Let's Encrypt YE1 → ISRG, Root YE → ISRG Root X2), not the more common RSA chain through ISRG Root X1. The MB2755's frozen firmware root store doesn't have a path to trust either one, and a firmware update didn't add one — so the fix is the same regardless of port: leave "Nie weryfikuj certyfikat" / "Don't verify certificate" disabled.

Docs and the case study page are updated: PRINTERS.md, DEVICE-CASE-STUDIES.md. Thanks again for taking the time to dig into this with openssl instead of just reporting "still broken."