We'd normally, wrote test for such PR but for such case, its a customer email and I cannot wrote such that specific test email with a "noname" file that has "application/pdf" type.

I think the most feasible and right way to do this is by splitting the test decrypt - an ambiguous file "noname" should not be recognized as an encrypted message and should be hidden in encrypted message into two, as the newer change should also fit for email const threadId1 = '18adb91ebf3ba7b9'; // email attachment "noname" with type img/<image-extension> and I believe it would not be part of that tests.

Hi @sosnovsky - this one is ready for a review. Thank you.

We'd normally, wrote test for such PR but for such case, its a customer email and I cannot wrote such that specific test email with a "noname" file that has "application/pdf" type.

It'll be useful to have such test, so in the future we won't break correct noname attachments parsing.
It should be possible to create such message with noname .pdf attachment by using Header Tools Lite extension for Thunderbird, it allows to edit message headers before sending.
Can you please try to create such message for test by removing name property from sending attachment?

Hi @sosnovsky, I tried your suggestion and it works flawlessly by using https://addons.thunderbird.net/en-US/thunderbird/addon/header-tools-lite/?src=search. This tool definitely helps a lot.

Hello @sosnovsky, I've added a test by crafting one. Please let me know if this looks good to you.