Port 110 is used by POP3, a protocol designed for downloading emails from a remote server to a local client. POP3 does not inherently synchronize changes (such as read status, folder organization, or deletions) between devices. The customer wants a more secure connection that automatically synchronizes with the server, which directly aligns with the functions of IMAP (Internet Message Access Protocol).

IMAP typically uses port 143 for unencrypted connections and 993 for secure, encrypted connections (IMAPS). It is designed for modern email usage—supporting multi-device access, live synchronization across clients, and server-stored mail. When a user reads, deletes, or moves an email using IMAP, these changes are reflected on the server and visible on every device logged into the same account.

CompTIA A+ emphasizes that IMAP is preferred for users requiring constant synchronization, mobile access, and cloud-based email management, while POP3 is considered outdated. IMAP also supports secure, encrypted communication when paired with SSL/TLS.

HTTPS and SFTP do not handle email retrieval, and SMTP is a sending protocol, not a retrieval protocol. Therefore, IMAP is the only correct and CompTIA-aligned upgrade option.