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Old 02-06-2012, 06:34 AM   #1
Registered: Jul 2010
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SMTP Relay.

Dear All,

I run a mailserver at home for 4/5 personal domains. Outgoing SMTP mail is relayed through my ISPs SMTP server due to my home IP being on a residential range and some recipient servers blocking email from my IP. This has until recently been ok, however recently proved quite flaky and I'm looking for somewhere else to relay through.

I have a dedicated server running Debian. How would I go about setting up a mailserver, not to host mail but merely to deliver the mail that is offloaded from my mailserver at home?

How would I ensure it is not an open relay?

Old 02-06-2012, 07:50 AM   #2
Registered: Jun 2007
Location: South Africa
Distribution: Linux Mint,Fedora, openSUSE, RHEL, SLES, Scientific Linux
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On your home MTA, and if you use postfix:

relayhost = [mailserver.isp.tld or an.ip.add.ress]
you could use that parameter to specify your ISP's SMTP server through which mail will be relayed by your home MTA. Don't forget the []'s

mynetworks =,
would be used to specify who your SMTP clients are so that you're not an open relay box.

Old 02-07-2012, 11:00 PM   #3
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Registered: Feb 2012
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If you use Exim, Here's the code that prevents it from being an open relay in the .conf

accept hosts = +relay_hosts
accept hosts = +auth_relay_hosts
message = authentication required
authenticated = *
deny message = relay not permitted

# default at end of acl causes a "deny", but line below will give
# an explicit error message:
deny message = relay not permitted
You can always check to see if it's an open relay by command line or using an online tool that checks it like this one..

Open Relay Test Tool


email, relay, smtp

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