Re: sendmail and blocked dynamic IP addresses

[Chris Hewitt <g0pae manordat demon co uk>]

Rick Stevens wrote:

> Jay Crews wrote:
>
> > Rick Stevens writes....
-------------------snipped--------------------

> > And I think I have even read on how to set up sendmail (sendmail.cf)
> > to fix this.
>
>
> Well, if you want the envelope address to be from jaycrews.com and if
> verizon is doing what I think they're doing, you can't.  If you can
> convince them that your system is legitimate and to accept such traffic,
> then you don't need to do anything.  The odds are that you won't, unless
> you switch to "business class". 

Even then it can go wrong. A large ISP here in the UK (not the one I'm 
with) decided that it would be a good anti-spam measure to no longer 
relay email from any domain that was not registered with them. (I'm told 
they also managed to not relay email for some domains that were). The 
stink when companies (their customers) suddenly found they could no 
longer send email was, well you can imagine.

> > Is this what masquerading is for?
>
>
> Yes, but all masquerading does is change the envelope sender to whatever
> the masquerade is.  To make your stuff go through, the envelope must be
> "something verizon net".  It won't appear to come from jaycrews.com. 

I've got a similar setup. All my computers here at home are on a private 
(not registered) domain and I masquerade (envelope and masquerade-all) 
as manordat.demon.co.uk so all email appears sent to and received from 
this. Although I do have a registered domain, I've not found a good way 
around this (without paying for a "business" account.

> > My original thought was to use my own SMTP to take traffic
> > of my ISP.  (Nice guy thing.) But hey......I'm fine using theirs.
> > I just want my mail to be received as, jpc jaycrews com
> > not blabla verizon net
>
>
> Can't be done with THEIR configuration or unless you tell them that
> your system is legitimate AND they allow it. 

I use my ISP's email server as my smart-host so all outgoing email goes 
via it. You can send email directly from your smtp server but some ISPs 
are now only accepting email from either other ISPs servers or you have 
to register your email server with them. I am told AOL is implementing 
this as an anti-spam measure.

> > When you say my ISP verifies me as a customer before relaying,
> > I assume it's from part/all of what I am sending them.  Is
> > it the complete email address?  (jpc jaycrews com)
> > The domain (jaycrews.com)?  Or just the username (jpc)?
>
>
> If you are sending mail as "something verizon net", they verify that
> the IP your data is coming from is on their network AND that the
> envelope sender has "@verizon.net" AND that the username you use is
> not a suspended account.  Remember, their rules will NOT permit you
> to send mail out through their servers UNLESS the envelope sender
> is "@verizon.net". 

If you are e.g. something mycomputer verizon net then all email for that 
subdomain is under your own control, you define users as you want. The 
check, as Rick says, is that a DNS lookup for mycomputer.verizon.net 
results in an IP address that they control. I've defined users for my 
children and recently one for the Fedora list, just create the new unix 
user and it works.

Regards

Chris