Thanks for your suggestions.
1) Automailer isn't supposed to be used as a massmailer. For massmailing Dolphin has a massmailer module. That is why that funciton is missing. However if for some reason you really needed to use it as a massmailer then you can use a small trick, by deactivating all automails except the one which must be sent right now and setting the time of the automailer's scheduler to the current time + 1 or 2 minutes, and then after 2-3 minutes reverting everything back.
2) Actually see more while sending to the external email it uses a site's address as From: field, i.e. address which was set at [admin panel -> settings -> basic settings]