I recently had someone (@comcast.net) try to email me (@gmail.com and @something.edu) including in their email 3 text files and a .docx file. The email never reached me and they never received any bounce message. I eliminated attachments one at a time and determined that one of the text files was causing the problem. Inspecting the text file, it appears to contain a number of non-ascii characters. I stripped out all printing ascii characters and newlines with the following command:
dcollins@laptop:~/Downloads$ tr -d "\012\015\040-\176" < filename.txt | od -x 0000000 e9e9 e9e9 e9e9 9595 9595 9595 9595 9595 0000020 9595 9595 9696 9797 9797 aeae aeae aeae 0000040 97ae 9797 9999 9999 9997 0000052
As you can see, the attachment contains several instances of
0x99. Shouldn't my mail program decide that this attachment contains non-ascii characters, base-64 encode it, and send it using MIME? I noticed that the other text attachments were transmitted as
Content-Type: text/plain, but since I didn't receive the problem attachment, I can't tell what my client did with it. Is this a bug in my client or in my ISP's mail server?