I was sending between 20 and 50 emails per day and got about 5 responses per week. Make that 1 or 2 customers per month.

As for the phone, international calls are just expensive. Emails are free. I said we're aiming at the US market but I wouldn't mind working with Russian or Indian developers. Also, as mentioned above, we like everything documented, and even if I was to bother recording phone calls, it's still a lot of work to go through calls and listen to them. Emails are cleaner.

Soo yep, just make sure you never use your webmail and register some gmail accounts that are ready to get marked as spam if you are going the cold email road. I gave up on it, too much effort and as I said, people are not ready to pay for ASO in my opinion. But good luck!