Problem
You would like to do a search for a specific LDAP attribute (ie email) using a file (emails.txt) with the list of emails you want to search for.
Solution
After exporting the password (LDP) you can use the following to do the search and output the results into a file (search_results.txt)
ldapsearch -LLL _H "ldaps://ldap_url:port" -D "cn=User_name" -w $LDP -b "ou=ou_name,dc=dc_name,dc=domain_name" -s sub -f emails.txt "(mail_attribute=%s)" uid mail_attribute other_attribute > search_results.txt