[exim] Testing sender and recipient domains in MIME ACL

I need to make business logic decisions in the MIME ACL on how to screen
MIME content based on the sender domain and recipient domain but the
variables that I need to not appear to be set up:

2020-05-18 16:05:04 1jahKC-0005Zn-Tj H=relay1.thorcom.net
[195.171.43.32] X=TLS1.3:TLS_AES_256_GCM_SHA384:256 CV=no
F=<test.user@???> temporarily rejected during MIME ACL checks:
cannot test domains condition in MIME ACL

Is there a reason for this?

Surely the HELO, MAIL and RCPT have run so these variables have been
determined and hence they could be inherited (passed to) the MIME ACL?

I can probably write a load of electric string go get round my use-case
by storing things in variables in RCPT ACL and then checking them in
MIME ACL but this seems somewhat ugly and complex.


Mike