I'm translating the signature for the email App into English. I want it short but correct!

I have tried different searches in Google and Linguee. However, none of the following possibilities seem popular on Google (and I don't find them on Linguee). So maybe none of the following options is correct?

• Email typed with a phone. Apologies for the briefness.
• Email written by phone. Apologies for the briefness.
• (and other combinations using the same words).

How do you actually write that sentence normally in a short way?