On Tue, Sep 02, 2003 at 06:51:59PM +0100, Colin Watson wrote: > Just wondering what this error (Helo Command Rejected: Host not found) was referring > too? I receive it in sendmail on messages I'm trying to fire off. I suspect (but > have been unable to confirm) it may be reverse DNS related?
Yes, probably. I suspect that this is the result of the latest move in the war-against-spam-and-viruses. A number of ISPs and other mail system administrators have developed a policy of being hard-line about the name a system uses to announce itself when connecting to their SMTP servers. Typically that is the argument to the 'HELO' or 'EHLO' command which is the opening line in the SMTP dialog. Some admins go even further and require that the name given in the HELO line corresponds to the IP number the connection was made from. The idea is that this name should be a fully qualified, resolvable domain name, or possibly an IP address. Generally that will automatically be the case if you're running one of the standard Unix MTAs on the open Internet, and have a correctly configured DNS zone file. However, if you're behind a NAT gateway or using a private DNS address space, then you might have trouble. With sendmail(8), you can override the default choice, which is just the FQDN of the server, by setting: define(`confDOMAIN_NAME', `smtp.example.com')dnl in your `hostname`.mc file. Note that this has nothing to do with what appears after the @ sign in any e-mail addresses dealt with by your server. It's effectively the hostname of the server itself that should be entered there. Cheers, Matthew -- Dr Matthew J Seaman MA, D.Phil. 26 The Paddocks Savill Way PGP: http://www.infracaninophile.co.uk/pgpkey Marlow Tel: +44 1628 476614 Bucks., SL7 1TH UK
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