EssentialPIM Pro has a powerful searching tool built in. It allows to search items through the whole database file with various conditions. Go to Tools -> Advanced search or press Ctrl+Alt+F to call Advanced search dialog:

Look in drop-down menu allows to set module to search, Include deleted items option includes/excludes items located in trash.

General and Advanced tabs allow to perform simplified or complex search tasks.

Time option can limit search period for items created or modified within the specified time frame.

Search under the General tab looks for the whole phrase typed into the Search for field. Search in fields drop-down list allows to narrow down the search area to subject, body or attachments fields only.

Advanced tab allows to set more complex search criteria:

First, you select field for one of the modules and then you select which of the conditions (is / isn't / contains /doesn't contain) to utilize. Once set, click on the Find Now button.