On Thu, 13 Nov 2003, Jack Coates wrote: > On Thu, 2003-11-13 at 14:06, Bill Mullen wrote: > > > Okay, I think you should at least change the "myhostname =" line, > > found in the /etc/postfix/main.cf file. Having the short hostname of > > your Postfix box here does you no good, as it is of utterly no use to > > the destination system. OTOH, if you changed it to "holt-tech.net", > > then at least the name resolves in one direction (forward), and agrees > > with the hostname in your MX record for the domain. It would still > > fail an rDNS check, though, if that check doesn't merely look for > > whether an rDNS entry exists, but goes further to insist that it match > > the stated hostname (which it won't). :( > > Luckily that's a pretty rare test as few ISPs or hosting companies will > make changes in rDNS for their customers. Lots of legit mail is blocked > when that test is used and eventually someone with some authority slaps > the wrist of the fool admin, who goes and sulks about how their clueless > management won't let them fight spam :-)
Yes, that is taking spam fighting to an extreme that breaks the acceptance of much perfectly valid mail. Throwing the baby out with the bathwater, as it were. :) Checking for the mere existence of an rDNS entry ought to be sufficient, IMHO, as that allows the recipient to identify the sending system to a reasonable degree of certainy. You don't need more than that, really. > > Bear in mind that the "myhostname =" setting in main.cf doesn't need > > to bear even the slightest resemblance to what your system actually > > calls itself; it is the string that is sent whenever Postfix > > identifies the system on which it is running to other systems (both > > clients and servers). As such, the value of this setting *will* have > > an impact on whether or not mail is accepted from you by some servers, > > as it is sent in the HELO/EHLO statement when Postfix initiates a > > connection as a client. > > > > If your external hostname (the one supplied you by your ISP, and > > currently "evrtwa1-ar17-4-35-151-034.evrtwa1.dsl-verizon.net") remains > > constant or nearly so, then *that* is the ideal string to put into > > main.cf as your "myhostname =" value, because then your name resolves > > in both directions. If you can do this, it mitigates a lot of problems > > of this variety. The mere fact that the hostname is obviously tied to > > the IP address should not be a deal-breaker in and of itself, even if > > you use DHCP, as many cable and DSL setups that use DHCP in fact > > change the IP address very rarely. > > if the address is in a DHCP pool assigned for home users, more and more > servers out there will block direct SMTP connections from it; only > relaying through the ISP's server will work in this case. Quite true, and one's best recourse in that situation is using the ISP's server as a relay, at least for the problem domains (I have to do that with a few). OTOH, that isn't what's happening to Michael, as his Postfix *can* send direct to the problem server(s), but only with certain clients having originated the message and given it to Postfix for delivery. Strange, isn't it? -- Bill Mullen [EMAIL PROTECTED] MA, USA RLU #270075 MDK 8.1 & 9.0 "In the beginning the Universe was created. This has made a lot of people very angry and been widely regarded as a bad move." - Douglas Adams
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