It is possible to add further parameters to your search in order to narrow it. You can limit a search by date with a "since. . . " predicate. Likewise, you can limit by sender and/or by the subject line with a "where . . ." predicate. For instance:

Search 'Digest=' in LSTOWN-L since 94/01/01
Search 'Digest=' in LSTOWN-L where sender contains 'Thomas'
Search * in LSTOWN-L where sender is ERIC@SEARN
Search * in LSTOWN-L since 94/01/01 where subject contains 'Digest'

are all valid search commands that will (depending on how well you've crafted your predicate) dramatically reduce the number of entries returned to you.