How can I configure my postfix server so reject_sender_login_mismatch doesn't block aliases of the main account?
I think you're looking for smtpd_sender_login_maps where you'll need to map the logins to aliases. See the official doxumentation on smtpd_sender_login_maps.
create a file called /etc/postfix/sender_login_maps
which contains mapped address
[email protected] [email protected]
edit /etc/postfix/main.cf
add below line
smtpd_sender_login_maps = hash:/etc/postfix/sender_login_maps
run cmd postmap /etc/postfix/sender_login_maps
restart postfix services