I sent my first email in 1975

My first job at IBM was as a vacation student working in the ROSS User's group, in RESPOND.
ROSS - Rationalised Ordering Support System
RESPOND - Retrieval Entry, Storage (and) Processing (of) Online Networked Data

I was a clerk and the only Brit in the department.
Every day I'd have to write a telex to coordinators in each European country advising them which 'cycles' had been processed overnight. A few months into the job I discovered the pleasure of using IBM golfball terminal/typewriters to use RETAIN (Remote Entry Technical Advice Information Network). I discovered that instead of hand writing telexes I could type them in myself and
send these to a pan-European distribution list.

Even though they were only being sent on the internal network these messages would now be considered emails.

I can't remember what I used to call them before I started sending PROFS Notes (we had been sending messages to/from TSO/VM ids well before PROFS/NOSS) but I still prefer using the term 'note' for a simple message, as opposed to 'document' for one written in Script/DCF.