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7. The mailing list remailer

7.1 Subscribing

The method of subscribing to each e-mail list is different, although most involve sending some kind of e-mail message. Please be very careful not to send to the replicating address of the mailgroup. This is a sure way to annoy the members of the list. Most remailers (but not all) have a separate address for subscribing. In confctrl, the administration address is as explained by

When you successfully subscribe you should (hopefully) see a welcome message in the newsgroup.

Some mailing lists do not let you subscribe an address you are not mailing from. In this case you will need to forge the return address of an e-mail.

7.2 Forging mail

Forgeing mail is easiest to do with an old Netscape client. It would accept anything for a return address. Fortunately, modern browsers require you to retreive mail successfully for an address before they will let you send. Thus, you are required to fall back the tried and true method....telnet.

Looking up MX hosts

When you speficy a web page, your browser does a DNS lookup to convert the domain name into an IP address. This is a lookup of an "A" record. (Also "CNAME" records are considered.) When sending mail a "MX" record is looked up. If this is missing a "CNAME" or "A" one is used. Thus, to forge mail you need to do an MX lookup.

dig mx
will give...
; <<>> DiG 8.2 <<>> mx 
;; res options: init recurs defnam dnsrch
;; got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 6
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 3, ADDITIONAL: 4
;;, type = MX, class = IN

;; ANSWER SECTION:                1D IN MX        0                1D IN MX        10

;; AUTHORITY SECTION:                1D IN NS                1D IN NS                1D IN NS

;; ADDITIONAL SECTION:            1D IN A         1D IN A             1D IN A           1D IN A

;; Total query time: 448 msec
;; FROM: to SERVER: default --
;; WHEN: Sun Jul 25 15:49:32 1999
;; MSG SIZE  sent: 25  rcvd: 182
thus you would use (If you don't have dig, nslookup will do.)


Mail is delivered using the Simple Mail Transport Protocol (SMTP). Like most good Internet protocols, it is ASCII based to make troubleshooting and development easier. I will not explain everything, but simply give an example. Hopefully, this is enough.

The protocol is line oriented. Each email as specified in RFC822, is composed of headers and body which are separated by the first blank line (no characters, not even spaces). SMTP specifies the end of an e-mail with a line containing only a period.

halyard$ telnet 25
Connected to
Escape character is '^]'.
220 ESMTP Sendmail 8.8.7/8.8.6; Sun, 25 Jul 1999 14:01:25 -0700 (PDT)
250 Hello howto@node-d8e9822 [] (may be forged), pleased to meet you
mail from:<>
250 <>... Sender ok
rcpt to:<>
250 <>... Recipient ok
354 Enter mail, end with "." on a line by itself
Subject: help

250 OAA26778 Message accepted for delivery
221 closing connection
Connection closed by foreign host.

7.3 Be patient

The mailing list is last because in part it is the slowest. When you mail to the reflected address, it may take up to an hour to see the response.

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