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I’ve recently built new mail qmail server with vpopmail to serve pop3 connectins and courierimap and courierimaps to take care for IMAP IMAPS.
I further used telnet to test if the Linux server pop3 service on (110) and imap on (143) worked fine, straight after the completed qmail install.
Here is how to test mail server with vpopmail listening for connections on pop3 port :
debian:~# telnet mail.mymailserver.com 110
Connected to mail.mymailserver.com.
Escape character is '^]'.
My first mail content retrieved with RETR commandgoes here ....
Connection closed by foreign host.
You see I have 5 messages in my mailbox, as you can see I used RETR command to check the content of my mail, this is handy as I can read my mails straight with telnet (if the mail is in plain text), of course it’s a bit more complicated if I have to read encrypted or html mail, though still its easy to write a tiny parser and pipe the content produced by telnet command to lynx or some other text based browser.
Now another sys admin handy tip is the use of telnet to check my mail servers IMAP servers is correctly operating.
Here is how:
debian:~# telnet mail.mymailserver.com 143
As you can see according to standard to send commands to IMAP server from console after a telnet connection you will have to always include a command line number like 01, 02, 03 .. etc.
Connected to localhost.
Escape character is '^]'.
* OK [CAPABILITY IMAP4rev1 UIDPLUS CHILDREN NAMESPACE THREAD=ORDEREDSUBJECT THREAD=REFERENCES SORT QUOTA IDLE ACL ACL2=UNION STARTTLS] Courier-IMAP ready. Copyright 1998-2010 Double Precision, Inc. See COPYING for distribution information.
01 LOGIN firstname.lastname@example.org here_goes_my_secret_pass
A OK LOGIN Ok.
02 LIST "" *
* LIST (Unmarked HasNoChildren) "." "INBOX"
02 OK LIST completed
03 SELECT INBOX
* FLAGS (Draft Answered Flagged Deleted Seen Recent)
* OK [PERMANENTFLAGS (* Draft Answered Flagged Deleted Seen)] Limited
* 5 EXISTS
* 5 RECENT
* OK [UIDVALIDITY 1312746907] Ok
* OK [MYRIGHTS "acdilrsw"] ACL
03 OK [READ-WRITE] Ok
04 STATUS INBOX (MESSAGES)
* STATUS "INBOX" (MESSAGES 5)
04 OK STATUS Completed.
05 FETCH 1 ALL
06 FETCH 1 BODY
07 FETCH 1 ENVELOPE
Using such a line numbering is not obligitory and also letters like A, B, C could be use still line numbering with numbers is generally a good idea since it’s easier for reading on the screen.
Now line 02 shows you available mailboxes, line 03 SELECT INBOX selects the imap Inbox to be further operated with, 04 STATUS INBOX cmd displays status about current mailboxes in folder.
FETCH 1 ALL instructs the imap server to get list of all IMAP message headers. Next command in line 05 FETCH 1 BODY will display the message body of the first message in list.
The 07 FETCH 1 ENVELOPE will display the mail headers for the 1 message.
Few other IMAP commands which might be helpfun on connection are:
08 FETCH 1 FULL
09 FETCH * FULL
First one would fetch complete content of a message numbered one from the imap server and the second one 09 FETCH * FULL will get all the mail content for all messages located on the remote IMAP server.
The STATUS command aforementioned earlier could take the following list of arguments:
MESSAGES, UNSEEN, RECENT UIDNEXT UIDVALIDITY
These commands are a gold mine for me as a sysadmin as it helps quickly solve problems, hope they would help to somebody out there as well 😉
This way is a way shorter than bothering each time to check, if some customer e-mail account is improperly configured by creating setting up a new account in Thunderbird.