mail-server Admin tasks on Postfix

We need a mail server expert to assist us with the following 3 tasks: Our setup is Postfix, Dovecot, Postfix Admin (for Admin UI), Roundcube (for Mail UI). We are using MySQL database for postfix. Our mail server is running on Debian 8 Linux OS. You need to login to our mail server via SSH to complete these tasks 1-Switch our primary mail domain name from [login to view URL] to [login to view URL] then remove the [login to view URL] 2-Setup an SMTP Rate-Limit to restrict our mail users from sending more than 150 emails per hr. Our users' are using simple passwords on their email accounts causing hacks and resulting in SPAM thereby reducing our IP reputation. The rate limit must be at a global level. 3. We need to set up a Smart Password Policy for our users to set for their email account that restricts them from the use of easy passwords. We like this type of Smart passwords policy. (min 8 alphanumeric characters, One CAP, One Special Character, One digit, and no sequential digits allowed). Notes: After the completion of each task listed, you need to test it making sure each task functions as expected. List the changes you made in our mail server within a word document. (File names, locations, and changes.)