When looking for emails from Mr. Mastin, please check spam folders as well. My mass emails are sent BCC to preserve email address privacy. Unfortunately, sometimes they are being picked up by spam filters.
When sending recordings to Mr. Mastin, please compress the files or record them at a lower setting. (You can access this from your device's settings under the camera options.) I have had success recording at 1080p HD at 30 fps. That setting yielded 2-minute videos for my Advanced Band students that were about 0.5MB in size. Another option would be to use an audio-only recording app, such as VoiceMemos. These create smaller size files. The trade-off is that not being able to see the student as well as hear them takes a teaching tool away.
Please have your child announce what song they are playing on the recording before they play it. This is especially helpful with beginners and if the name of the song is not in the file name.