mailinabox global rate limit

sudo apt-get install postfwd

sudo nano /etc/postfix/postfwd.cf

Clear any default examples and add the following rule to limit authenticated users to 99 emails per day:

# Limit authenticated users to 99 emails per 24 hours (86400 seconds)
id=RATE_LIMIT_USER; \
    sasl_username=~./; \
    action=rate(sasl_username/99/86400/REJECT You have exceeded your daily quota of 99 emails);

sudo systemctl restart postfwd
sudo systemctl enable postfwd

sudo nano /mailinabox/setup/postfix.sh

Scroll down until you find the section configuring smtpd_sender_restrictions. It typically looks like this:

tools/editconf.py /etc/postfix/main.cf \
    smtpd_sender_restrictions="permit_sasl_authenticated,permit_mynetworks,reject_non_fqdn_sender,reject_unknown_sender_domain,reject_unlisted_sender"

Modify that block to append check_policy_service inet:127.0.0.1:10040 right after permit_sasl_authenticated. This ensures postfwd checks authenticated users before they are completely cleared to send:

tools/editconf.py /etc/postfix/main.cf \
    smtpd_sender_restrictions="permit_sasl_authenticated,check_policy_service inet:127.0.0.1:10040,permit_mynetworks,reject_non_fqdn_sender,reject_unknown_sender_domain,reject_unlisted_sender"

Run the Mail-in-a-Box setup script to safely regenerate your live Postfix configurations with the new policy rule injected.