[Exim] Where to put 'acl_smtp_data' section?

Hi.

I'm trying to add an acl_smtp_data section to my exim.conf to block out
certain mail. Should I add the acl_smtp_data under "begin acl"? And if
so, before or after 'acl_check_rcpt'?

I tried searching the Exim specification (I'm running 4.10 on Linux) but
I couldn't find anything on acl_smtp_data.

Any pointers would be appreciated.

Thanks,

Erik.