Can multiple terminals use SendNotification to send notifications all to a single instance of MT4 mobile running on an iphone or android phone?
Let's say we have Terminal A from Broker 1, Terminal B from Broker 1, Terminal C from Broker 2...
can it be set up so they all send notifications to the same phone?
Yes but you have to use alternative communication channels.
Or the SendMail() function then they can all send to the same email address.
Yes, multiple MT4 terminals can send notifications to single MT4 mobile instance using SendNotification() without a problem. No need to use e'mail. Just use the same Metaquotes ID in settings of every terminal.