Which TCP/IP protocol for email download allows several clients to connect to the same mailbox at the same time?

The Internet Message Access System (IMAP) is a secure protocol for downloading email. It has various advantages over the previous Post Office Protocol 3 protocol (POP3). First , IMAP4 operates in both connected and disconnected modes. Second, unlike POP3, it allows you to save your email on the server rather than downloading it. Third, IMAP4 allows several clients to connect to the same inbox at the same time. For sending email, Simple Mail Transfer Protocol (SMTP) is utilized, while Server Message Block (SMB) is used for file sharing across a network.