Date: Tue, 23 Jun 1998 17:38:29 -0700 (PDT) From: patl@phoenix.volant.org To: drmarsh@bigfoot.com Cc: FreeBSD-Questions List <freebsd-questions@FreeBSD.ORG> Subject: Re: sendmail: How do I make sendmail 'fake' my 'online' mail address? (fwd) Message-ID: <ML-3.3.898648709.495.patl@asimov> In-Reply-To: <199806232251.XAA02175@bigfoot.com>
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> > It should always correctly identify itself as your host in your > > domain. And most knowlegable email gurus agree that header rewriting is > > generally a Bad Idea. (Some claim it is downright evil.) > > Which host do you mean here? > I have an (obviously) bogus 'domain' for my machine, just for the purpose > of giving it a name (which is currently appearing in my news headers, more > manual reading in order, I think ;-) but I don't have a static IP > address with my ISP, and so I'm allocated a random dialup-xxx.zetnet.co.uk > address each time I connect. Using bogus domain names for machines which are even intermittantly internet-connected is not generally a good idea. You might want to see if ZetNet will give you a fixed host or subdomain name. It doesn't have to be bound to a specific IP address as long as they have an MX record for it that points to one of their servers that will hold your mail until you dialup and ask for it. You would still get the dialup-xxx name when you connect; but you would also have the fixed name. (Although they probably won't be able to give the fixed name an IP address when you are logged in.) This would be the easiest, and probably cheapest solution; if it is available. Another solution would be to register your own domain name, with ZetNet acting as the primary (and possibly secondary) for your DNS records, including an MX record pointing to one of their servers. If you don't want the expense of your own domain, and ZetNet won't set up a fixed host or subdomain for you; you could arange with a third party to use a subdomain within their domain. The problem with any of these solutions is that without a fixed IP address, your outgoing mail will fail a reverse DNS lookup; and may still be mistaken for SPAM. To avoid this, you need to set up your MTA so that it doesn't try to directly deliver any external mail. Instead, it should simply simply say "Hmm, this isn't for the local host (or LAN), let's pass it up to ZetNet's mailer and let it handle it." (Then it will be the ZetNet mail server contacting the remote host. Their server should have a fixed IP address and all of the necessary DNS records to pass simple SPAM/forgery checks.) BUT I just took a step back from the immediate difficulties and got a better view of the root problem. (We're here to drain the swamp. The alligators are just an annoyance...) The good news is that you may have an even easier solution that doesn't require any MTA setup at all. If you have a single host, and you don't need to compose and store the outgoing mail locally until the next dialup connection, you may be able to simply tell your MUA to use the ZetNet mail server for outgoing messages. It has been a long time since I looked into elm; so I have no idea whether it can do that or not. Traditional unix MUAs will tend to simply invoke a local copy of sendmail or /bin/mail and assume a local SMTP daemon; but some of the newer MUAs let you specify another host, and often a non-standard port, for outgoing SMTP service. (This is particularly common among MUAs that are designed to work with IMAP or POP3 servers rather than just your local unix mailbox.) Netscape Communicator and ML both allow you to specify the SMTP server separately from the POP/ IMAP server(s). > I may consider looking into this, once I get sendmail working properly > at any rate! See http://www.exim.org/ for more info. Since you are running FreeBSD, it is an easy install from the ports collection. > > > MASQUERADE_AS(`bigfoot.com')dnl > > > > This is intended to be used on a central mail server to make all > > mail from within the domain appear to come from the domain itself > > instead of from individual machines. It is -NOT- intended to be > > used to pretend to be from another domain entirely. > > Ah. Again it's based on my reading of the FAQ! Maybe the FAQ entry is > a little unclear. The thing to remember about FAQs is that they tend to be aimed at the most common case. (Or at least the case that was thought to be the most common when the FAQ was written...) You need to read between the lines to discover the implicit assumptions and figure out where they diverge from your specific needs. > I take it I should remove this line completely? In your setup, I'd say yes. If you get a (sub)domain of your own, and you have more than one machine on your side of the dial-up, you would probably want to change this line to be your (sub)domain to hide the individual hosts. > > > FEATURE(masquerade_envelope)dnl > > > EXPOSED_USER(root) > > > FEATURE(mailertable, `hash -o /etc/mailertable')dnl > > > FEATURE(nodns)dnl > > > FEATURE(nouucp)dnl > > > define(`confCW_FILE', `-o /etc/sendmail.cw')dnl > > > define(SMART_HOST, `mail.zetnet.co.uk') > > > Dm bigfoot.com > > > define(`confDOMAIN_NAME', `bigfoot.com')dnl > > Do you have any idea which (if any) of these lines I should or must remove? > Presumably the masquerade_envelope isn't needed if I don't have the > MASQUERADE_AS line? I'm rather unsure about: I'd have to re-read the Sendmail book to have a clue - it's been several years since I switched to exim; and the details of sendmail configuration can fade pretty fast... 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