I have checked postfix related questions for my issue but nothing seems to work. I would like to relay emails to only specific domain so that our clients do not received our dev emails. I have used “access” , transport but nothing seems to work. I have tried these links
transport

i have used REJECT and discard as well in access and transport. Moreover in my main.cf i used following

smtpd_recipient_restrictions =
hash:/etc/postfix/access
reject

for transport, i created a transport file and have these entries

example.com    :
.              discard

this does not work, however in same transport file, if a put a domain like reject.com discard it will work, but i want to block all other domains, and only allow example.com