On Fri, 2007-06-15 at 17:57 +0200, Renaud Allard wrote: > > Leonardo Boselli wrote: > > Some user had voicely complained me that one of thetir correspondent > > (say [EMAIL PROTECTED] -fictitious-) has all his e-mail rejected. > > I checked and turned that the server, that officially has the name > > mail.ditchedserver.org, send this helo: > > HELO ISCRA_domo.arsi > > (and this name is the real one that send !) > > > > my exim 4.63 is unhappy and reject immediately the connection saying there > > is an illegal (I suppose '_' )characther in helo name. > > [chop] > > > > In alternative: can some one give me a link to some offical rule saying is > > not acceptable sending Helo with underscores or non existant FQDN ? > > > > Hello > > quoting RFC2821 paragraph 4.1.2: > In > particular, the underscore character is not permitted. SMTP servers > that receive a command in which invalid character codes have been > employed, and for which there are no other reasons for rejection, > MUST reject that command with a 501 response.
In addition, underscores are illegal for host names on the internet, as per <URL: http://tools.ietf.org/rfc/rfc952.txt>. Underscores are now used for special purposes within DNS (like SRV records), but should never appear in a real hostname. The main problem is that some operating systems allows setting the hostname to a name with an underscore. Which is well and fine as long as you don't connect to the Internet. These guys will see a whole bunch of problems for any service that wants to look up their hostname due to this. Or rather, the remote users will see the problems. > If you wish to accept them, you can put in your config: > helo_allow_chars = _ That won't help if using helo_verify and the DNS is (correctly) rejecting queries for hostnames containing illegal characters. Regards, -- *Art -- ## List details at http://www.exim.org/mailman/listinfo/exim-users ## Exim details at http://www.exim.org/ ## Please use the Wiki with this list - http://www.exim.org/eximwiki/
