sending mp3s from my notes do not playback when emailed or messaged to recipients

I’m a songwriter, My Apple studio computer is synced to my phone, so when I create an mp3 from my Digital Audio Workstation, I simply paste It on a note containing the lyric.

It immediately goes to my iPhone, and I can Listen and continue work on the Song. However if I try sending that mp3 from my notes, the recipients often cannot play it back.