[Exim] ldap lookups from system filter ?

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Hi,

I'm having trouble getting a ldap lookup to work from a system filter. This is the code that's in my filter:

[...]
if (${lookup{"test"}ldap{ldap://localhost/cn=${quote_ldap:"test"},dc=test,dc=us}} contains "a" ) then
[...]

All attrempts to run and test this with the -bF option return the error message:
Filter error: unrecognized condition word "ldap" near line 20 of filter file

Anybody got any ideas what the syntax should look like ?
Thanks and regards

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