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On Thu, 2 Jul 2009, Julian Hall wrote: > Brad Rogers wrote: >> On Wed, 01 Jul 2009 23:16:08 +0100 >> Simon Robert <simon.robert@xxxxxxxxxxxxxxxxxxxxxx> wrote: >> >> Hello Simon, >> >>> Has anyone else run into the problem of an ISP refusing to send out >>> mail which does not use their own domain? >> >> I thought most of them did that. >> > That's what I thought when I read the first email. Open Relays are a > gift to spammers, which is why most (if not all) ISPs will not forward > mail that doesn't use their SMTP server. Rereading again I think that's > slightly different from what Simon said. ISPs *should* forward email > using *addresses* not on their domain provided the mail is sent through > their SMTP server. For example my ISP Virginmedia carries all email > from my domain, but I use *their* SMTP server smtp.ntlworld.com. > BAscally the SMTP server used needs to be the same as the domain used to > connect to the internet (AFAIK). Traditionally (or rather, after c1995), a connectivity ISP would know their own IP addresses, so allow customers connected to them to relay email based on their connection IP address. This is still the case for many connectivity ISPs. However - to "protect" themselves from customers PCs having rugue spamming software installed a few are moving to blocking direct outbound port 25 connections and either warning their users (Orange), or forcing them through their own email servers. For the most part, this is fine, however a recent development is when forwding them through their own servers, to check the sending email address and if it's not an approved one, then they block it. An added hassle is when the smart people have bought their own domains and are using an ISP independant of their connectivity ISP to send and recieve email. The connectivity ISPs who block/divert outbound port 25 connections block access for these people. So for now, switching to using port 587 seems to work, and any standards compliant email server ought to be listning on port 587 as well as port 25. I'm sure BT retail, etc. will cotton on to this soon though, then we'll just have to ssh/etc. tunnel our way out and be damned. One could argue that this sort of interception breaks net neutrality, (as well as a whole load of rfc's and the basic operating principle), but then that's something we do not have in the UK. Gordon -- The Mailing List for the Devon & Cornwall LUG http://mailman.dclug.org.uk/listinfo/list FAQ: http://www.dcglug.org.uk/linux_adm/list-faq.html