IMAP command
openssl s_client -connect imap.163.com:993 -crlf
A0011 LOGIN 15313xx57@163.com xx
A002 LIST "" "*"
A003 SELECT INBOX
A004 FETCH 1 FULL
A005 FETCH 1 BODYSTRUCTURE
A006 FETCH 1 BODY[TEXT]
A007 FETCH 1 BODY[1]
A008 FETCH 1 BODY[1.1]
A009 FETCH 1 BODY[1.2]
A010 FETCH 1 BODY[2]
A011 LOGOUT

https://www.cnblogs.com/abiao/articles/3272549.html

imap获取未读邮件数量--------139----------
1 capability   
2 login "15313153337@139.com" "xxx"
3 select inbox
* 35 EXISTS
* 1 RECENT
* OK [UNSEEN 35] Message 35 is first unseen
* OK [UIDVALIDITY 1] UIDs valid
* OK [UIDNEXT 2746] Predicted next UID
* FLAGS (\Answered \Seen \Deleted \Draft \Flagged)
* OK [PERMANENTFLAGS (\Answered \Seen \Deleted \Draft \Flagged)] Limited
4 OK [READ-WRITE] select completed


--------gmail----------

telnet imap.163.com 143
* OK Coremail System IMap Server Ready(163com[10774b260cc7a37d26d71b52404dcf5c])
1 capability
* CAPABILITY IMAP4rev1 XLIST SPECIAL-USE ID LITERAL+ STARTTLS XAPPLEPUSHSERVICE
UIDPLUS X-CM-EXT-1
1 OK CAPABILITY completed
2 login "xxx" "xxx"
2 OK LOGIN completed
3 select INBOX
3 NO SELECT Unsafe Login. Please contact kefu@188.com for help
4 SELECT INBOX

A3 uid fetch 1:* flag(size uid)　

3 UID fetch 1:* (FLAGS)


A1  uid fetch 1 body.peek(1)

A7 FETCH 1 (BODYSTRUCTURE)

C6 XLIST "" "*"
* XLIST (\Inbox) "/" "INBOX"
* XLIST (\Drafts) "/" "&g0l6P3ux-"
* XLIST (\Sent) "/" "&XfJT0ZAB-"
* XLIST (\Trash) "/" "&XfJSIJZk-"
* XLIST (\Spam) "/" "&V4NXPpCuTvY-"
* XLIST () "/" "&dcVr0mWHTvZZOQ-"
* XLIST () "/" "2222"
* XLIST () "/" "3333"
* XLIST () "/" "666"
* XLIST () "/" "bigfolder"
* XLIST () "/" "&le6YmA-"
C6 OK XLIST Completed