apg is a handy utility for creating random passwords / strings. To install it run:
apt-get install apg
The below for loop will create 300 random usernames / email addresses in the format firstname.lastname@example.org. You can always replace “domain” with “$i” , then you’ll have addresses in the format email@example.com.
-M – specifies that mode will be used
L – use small letters only mode
-n – number of passwords/random strings, in this case 300
for i in $(apg -M L -n 300); do echo $firstname.lastname@example.org >> fileToSaveResult ; done