Limit mails per day by user (not domain)?

I notice that Email Settings → Message Rate Limiting edits this file:

/etc/milter-greylist/greylist.conf

As an example in this way:

ratelimit “domain_1818531472109143” rcpt 50 / 24h
racl blacklist from /.@testdomain.com/ ratelimit “domain_1818531472109143” msg “Message quota exceeded”
racl whitelist from /.
@testdomain.com/

That syntax (specifically “from /.*@”) looks like it might lend itself to a single-address too, somehow. If so, what is the syntax and logic?

For example would:

racl whitelist from /special-exception@testdomain.com/
ratelimit “domain_1818531472109143” rcpt 50 / 24h
racl blacklist from /.@testdomain.com/ ratelimit “domain_1818531472109143” msg “Message quota exceeded”
racl whitelist from /.
@testdomain.com/

Work to create a special exemption to the rule for one particular user? (And does it work by reading-down the file till it gets a hit, or could I put a line like that anywhere in the file?)

SYSTEM INFORMATION
OS type and version Ubuntu 22.04
Virtualmin version 7.10.0