Above message should appear only when:
- You are performing a search for an exact phrase (between double quotes) inside the body.
- Potential messages to be opened to search for the exact phrase (after applying all other search criteria) exceeds configured limit value (20 by default).
To be able to complete these searches you can increase this limit value, which is stored in the sys_config table of ASM database; you can run for example following SQL query on the database itself (replacing N with new desired value):
UPDATE sys_config
SET cfg_value = 'N'
WHERE cfg_id=33
GO