IMAP (Internet Message Access Protocol) is an advanced protocol for receiving E-mails. It is a method of accessing E-mail messages stored on a mail server.
Unlike POP3 where all E-mails are downloaded to the computer/mobile device and completely removed from the mail server, IMAP simply downloads a copy of the E-mails. This is convenient as the E-mail account can be set up on multiple computers and devices using IMAP. The original E-mail will always remain on the mail server.
If a personal computer or mobile phone that was configured to be the primary means of checking E-mail/malfunctions is lost, stolen or inoperable, the E-mails will not be lost. Set up the account using IMAP on another computer or device or simply check 1&1 WebMail. All E-mails remain intact.