This appeared on the AOL-LIST-OWNERS listserv: I frequently get cases where people can't post to the list because the listserv doesn't recognize the sender. I'd like to have a standard response which I send out in these cases, which explains the situation so that an e-mail novice can figure out how to talk to a network manager about the problem, and trouble-shoot it. Has anyone else prepared such a form letter? Before I could attempt to write one myself, if needed, I'd need to understand the problem a bit better. Which field in the message header does the listserv look at to see if it recognizes the sender. The "from" field? "Reply-to"? "Sender"? I'm conscious of this, because I often send mail from my bway.net account (where I am "[log in to unmask]" but use "[log in to unmask]" as the "reply-to" address. [I don't use bway.net to post to listservs]. Which one does the listserv use to decide if this is a legitimate poster? Which one appears in a listserv digest, for example, as the "from" field? While we're at it, can anyone explain to me what a firewall is and how it relates to these issues? Thanks. Harriet Bograd, Attorney/Consultant <[log in to unmask]> Nonprofit Coordinating Committee of New York Coordinator, Cyber-Accountability Listserv (to join, e-mail [log in to unmask]) Web site: http://www.bway.net/~hbograd/cyb-acc.html