My app creates mails with attachments, and uses an intent with Intent.ACTION_SEND to launch a mail app.
Intent.ACTION_SEND
It works with all the mail apps I tested with, e
I tested it and I found out that it was definitely private storage access problem. When you attach some file to Gmail (over 5.0) do not use the file from private storage such as /data/data/package/. Try to use /storage/sdcard.
You can successfully attach your file.