From kitploit.com
IMAPLoginTester is a simple Python script that reads a text file with lots of e-mails and passwords, and tries to check if those credentials are valid by trying to login to the respective IMAP servers.
IMAPLoginTester – Script That Reads A Text File With Lots Of E-Mails And Passwords, And Tries To Check If Those Credentials Are Valid By Trying To Login On IMAP Servers