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Robin Becker wrote:
> these all sound very reasonable. However, we use the same IP for several
> virtual hosts ie we have more than one domain name so the reverse DNS is
> not clear to me. Is the from address inspected for comparison with the
> RDNS ie if I claim to be sending from xxx.com should my RDNS point back
> to xxx.com? Presumably I can have only one IP-->domain ptr. I suspect it
> will be easier to set up the front end machine as that is supposed to be
> for the same client.
Supporting several e-mail domains on one server is not a problem.
There is no general requirement that the mail server for a domain
'foo.com' have an address within foo.com --- you can quite freely
have your e-mail handled by a third party.
The important things to make sure of are:
* Your mail server HELOs with a valid domain name, and that
domain name should correspond to the IP that the mail server
connects as, both forwards and backwards. Note: 'connects as'
-- if your mail server is behind a NAT gateway, you will have
to take that into account in your configuration.
* Don't use the sort of domain name that is a thinly disguised
IP number: eg: host12-34-56-78.provider.net -- this sort of
hostname is a pretty good diagnostic for a spam source and
some mail admins will go as far as immediately rejecting
messages from such addresses.
* Don't use addresses from dynamic IP number pools used for
residential ADSL services. These overlaps a great deal with
the above, and are frequently rejected for much the same sort
of reasons. (There are entire RBL lists dedicated to enumerating
such residential IP address blocks).
* Do use static IP numbers from ranges specifically allocated to
you.
* Do make sure that you provide appropriate SPF records with
include the name / IP your mail server HELOs as. Or if you
aren't a believer in SPF, then either use a neutral entry like
"v:spf1 ~all" or no entry at all.
* Make sure that [EMAIL PROTECTED], [EMAIL PROTECTED]
and possibly a few other common addresses are accepted by your
domain, the messages are read and acted upon promptly. You should
exempt these addresses as far as possible from all forms of
anti-spam filtering.
Cheers,
Matthew
- --
Dr Matthew J Seaman MA, D.Phil. 7 Priory Courtyard
Flat 3
PGP: http://www.infracaninophile.co.uk/pgpkey Ramsgate
Kent, CT11 9PW
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