TCP- Transmission Control Protocol
IP- Internet Protocol
IMAP (Internet Message Access Protocol)
is a standard email protocol that stores email messages on a mail server,
but allows the end user to view and manipulate the messages as though
they were stored locally on the end user's computing device(s).
IMAP by default uses TCP port 143.
Simple Mail Transfer Protocol (SMTP)
is an Internet standard for electronic mail (email) transmission.
SMTP by default uses TCP port 25.
SMTP is used only for sending messages, while IMAP (and POP3) are used to both send, receive, and read email messages.
IMAP uses port 143,
SSL/TLS encrypted IMAP uses port 993.
POP uses port 110.
SSL/TLS encrypted POP uses port 995.
SMTP uses port 25.
SSL/TLS encrypted SMTP uses port 465 .