Which TCP/IP port will an email client utilize to send email to its email server?

The Simple Mail Transfer Protocol is used to send emails from clients to servers (SMTP). Port 25 is used by SMTP. Think "S" for "Send" while trying to recall whether SMTP is sending or receiving email. Telnet used Port 23, which is currently deemed unsafe and obsolete. POP3 (Post Office Protocol 3) and IMAP (Internet Mail Access Protocol) use ports 110 and 143, respectively, to retrieve email.