[Mobhack]

Are you sending your pair of files to him compressed (zip, rar whatever)?

If so - what is he using to uncompress the files?. We did have a case a decade or more back where one guy was using some sort of unzip utility that did not properly service zips made by whatever the sender was using. When both used the same freeware zip utility, then end of problem.

If it is some random google app, or the Windows filesystem (which thinks it knows about zip files, and tries to show them as folders... ) rather than a properly designed compression utility like 7zip, winzip etc then that could be the problem.

If you are not sending the files compressed, but as simple email attatchments - then google mail and other email checker things can bork the attatchments. Compress with a real file compression utility, attatch and send.

And email and anti-whatever can still bork your email sending even with properly compressed files. I often have to rename .zip files to .piz when sending to DRG, or use .7z format since every few months or so his ISP's email filtering decides to bounce any email with a zip file, or bounce zips containing EXE inside, or rars and so on. Usually lasts a couple of weeks, then clears. Renaming to .piz worked some time back, now if it gets huffy it seems to bounce those too (is probably now reading the file header, not the extension name) - but .7z format did not seem to be on its watchlist (yet!).