Here's one of the subscription replies that I got from one of the listserv lists. It goes into pretty good detail of how it handles the verification and the time frames that it implements. I've also tagged one of their sig lines that the list adds to all messages at the bottom.
The way they are setup, you pretty much have to be where your address says you are from, for you to get subscribed to the list.
From: Brock Rozen[SMTP:brozen @
Sent: Monday, January 22, 1996 8:20 PM
To: Dan Tucker
Cc: list-managers @
Subject: Re: 3rd party auto-reply mailing list attack
I've seen a similar system, but it wasn't majordomo.
All they had to do was reply to the message with the word OK
If they had a weird system and couldn't reply to the message but had to
send another message or something, they could reply with OK <validation-code>
and thus the system knew it was them....
The system I used was listserv @
From: L-Soft list server at PEACH.EASE.LSOFT.COM (1.8b)[SMTP:LISTSERV @
Sent: Monday, January 08, 1996 11:18 PM
To: Ed Woodrick
Subject: Command confirmation request (612F07)
SUBSCRIBE WIN95-L Ed Woodrick
has been received. You must now reply to this message (as explained
below) to complete your subscription. The purpose of this confirmation
procedure is to check that the address LISTSERV is about to add to the
list for your subscription is reachable. This is a typical procedure for
high-volume lists and all new subscribers are subjected to it - you are
not being singled out. Every effort has been made to make this
verification as simple and painless as possible. Thanks in advance for
To confirm the execution of your command, simply reply to the present
message and type "ok" (without the quotes) as the text of your message.
Just the word "ok" - do not retype the command. This procedure will work
with any mail program that fully conforms to the Internet standards for
electronic mail. If you receive an error message, try sending a new
message to LISTSERV @
COM (without using the "reply"
function - this is very important) and type "ok 612F07" as the text of
Finally, your command will be cancelled automatically if you do not
confirm it within 48h. After that time, you must start over and resend
the command to get a new confirmation code. If you change your mind and
decide that you do NOT want to confirm the command, simply discard the
present message and let the command expire on its own.
The WIN95-L list is hosted on a Windows NT(TM) machine running L-Soft
international's LISTSERV(TM) software. To unsubscribe, send a SIGNOFF
WIN95-L command to LISTSERV @
If you have ques-
tions about the list, write to WIN95-L-REQUEST @
For LISTSERV sales information, just write to SALES @