How do I search for specific subscribers?

Go to the newsletter’s dashboard.

Look for the text box under Subscriber Management and use the search feature.

Once there, you enter your search criteria.  The search match works from the left of each subscriber’s email address, so a search for phil will match and but NOT
You can use the asterisk character as a wildcard, matching any number of characters. For example, a search for p* will match all your subscribers at AOL whose email addresses start with a p. All searches have the wildcard character automatically appended, so a search for phil is, in effect, a search for phil* – you don’t have to specify the trailing *
You can also use multiple wildcard characters. So a search for phil*@*.net is a valid search query.
CAUTION: If you use the * wildcard, know that the further to the left the asterisk appears the slower the search will be, and searches are especially slow if you have an asterisk as the first element of your search string.  Try to be as specific as you can be on your first attempt.