imap telnet session

connect

clear-text

telnet IMAP_SERVER 143

starttls

    openssl s_client -starttls imap -connect IMAP_SERVER:143 -quiet -crlf

implicit ssl

    openssl s_client -starttls imap -connect IMAP_SERVER:993 -quiet -crlf

more options

# -tls1
# -tls1_2

proceed

    1 login TEST_ACCOUNT PASSWORD
    1 list "" "*"
    1 logout

troubleshooting

you need -crlf to talk to an Exchange server