MacOS stock Mail app | Some attachments cannot be downloaded when their filename contains Greek characters

SakisAg wrote:

So, since the Gmail web version shows the attachment filenames correctly, I would assume the problem to reside with the sch.gr email provider not doing something properly (maybe a server side misconfiguration). On the other hand Gmail manages to see through the issue for its web version of their service, but Mail app doesn't when it receives the emails. Rather peculiar, correct?

Actually not very peculiar. I’ve seen similar things before. The most likely cause is an encoding problem. Apple is usually more strict about these things. And because Apple users are more insular, and less business-focused, problems like this aren’t encountered as often and aren’t supported. Other companies with different markets, namely Google and Microsoft, are going to be accepting of these encoding problems. And since they are more accepting, there is less incentive on the originator of the corrupt data to fix the problem.

This problem exists, to one degree or another, throughout the internet and the computing industry. Different companies have different standards about when to stand their ground and refuse to accept invalid data. E-mail messages are particularly problematic. Apple, because of its market, it’s relatively small market size, it’s relatively large market power, and it’s own quirks, is more likely to reject corrupted data like this than other companies. So when you encounter an edge case like, with email attachments written in Greek, it’s not surprising that you would be able to see it fail.

If you could anonymize the e-mail and post it, I could tell you exactly what is wrong with it. But in all honesty, it’s a waste of time. If it is an Apple bug, Apple isn’t going to fix it. If it isn’t an Apple bug, Apple isn’t going to fix it. You would also have to track down who actually encoded the e-mail incorrectly. Maybe it was the sender’s e-mail client. But it could have also been any e-mail server between the sender and you. It isn’t unusual to disassemble e-mails to check them for viruses, phishing, etc., reassemble them, and send them on. There is no guarantee they will be reassembled correctly.

SakisAg wrote:

In conclusion, this is what leads me to deem it as an Apple bug.

Perhaps Apple implemented more lenient checking on iOS? Regardless, I never discounted the possibility that it could be an Apple bug. I simply said that Apple isn't going to fix it, at least not directly. Apple may very well replace the current version of Mac Mail for the iOS version at a future date. Maybe that will fix this bug. Maybe that will introduce new bugs. But without seeing the original message, I will continue to assume that the message was simply encoded incorrectly.

Perhaps Apple Mail extracts and caches the attachments, correcting the encoding in the process. That might explain why you see it correctly when you switch to a different message. MIME e-mail is simply exceptionally difficult to compose. A significant portion of all e-mails that we all use on a daily basis is the result of some company deciding to abandon existing standards and make up a new one. It caught on and now we have HTML e-mail.

This sample looks fine in Apple Mail. Do you experience the problem with it? I'm just opening the file as an "eml" file. I didn't try to send it to myself like a real message.

I looked at the content and it appears correct. There is no problem in using different encodings, including iso-8859-7, as long as the content is correct.

This part can be a little tricky. This is getting pretty deep into the details of MIME encoding by using a "B-encoding" in a content-disposition field. It appears to be correct and Apple Mail appears happy with it. But just because one does something correctly doesn't mean they won't be punished for it. Various spam filters and e-mail gateways could corrupt this data.

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