The EA MT4 should read the Email  which contents all the Position informations and execute it.
The EA should be able to read the following information and place the trade: 
Email body example: 
Signal_id: 32154, 45687, 42561
side: Buy
instrument: EURUSD
lotsize: 0.1 fix or from Balance % lost per trade calculated with SL
take_profit: 20
stop_loss: 20
trailing_stop: 5, 10
close_after: 60
comment: text


-Signal_id
This Id gives the EA the Information that it should trade. So i should choose one or more Signal_id’s that the EA knows what Email is to trade and what not. 


-Buy/sell


-Instrument


-Lotsize 


-TP and SL  (as Pips difference or as exactly point )


-Trailing Stop (the distance should also be individual)


-enabling Trailing Stop Loss (will be activated/triggered after a trade gains this number of pips) 


-Close trade after x minutes if TP or SL not reached.


-Trade comment  
 
If in the Email  is not set all informations where should be a option for automatic setting of the informations which are not given.