Constrain input to a few different strings
Change your constraint to 

CHECK (type IN ('email','post','IRL','minutes'))


This will be converted by the parser into:

CHECK (type = ANY( ARRAY['email','post','IRL','minutes']))


That should do what you are looking at.

However I have to wonder if it wouldn't be better to do this:

CREATE TABLE comlog_types (
     type text
);


And then add a foreign key to enforce the constraint.  This would make it easier to add types in the future.