Email using shell script using email address from external flat file

I'm using alexkowalski script from Email using shell script

MAILADDR=(mail1@example.com, mail2@example.com, mail3@example.com)
for i in "${MAILADDR[@]}"
    do
         echo "Mail test..." | mail -s "Mail test subject..." $i
    done

My question is how to read MAILADDR array from an external flat file?

And how to insert an external flat file replacing the body of the email as in

echo"/home/user/information-for-any-user.txt"  | mail -s "Mail test subject..." $i ??