Securing Open Relays

How to prevent unauthorized third-party mail relaying through your mail servers.

Vendor Page	Advice to Help Secure the Relay	Vulnerability References
Deliberate Open Relay	SpamTrap - a less than perfect solution	CVE-1999-0512
Generic Open Relay	MAPS: How to secure your mail system against third-party relay - mirrors: 1 JANET: Repairing open mail relays (JANET Mailer Shield) Securing and testing servers SMTP servers may third-party relay UUCP style addresses Third-Party Mail Relay – An Email Threat - PDF	XFDB-210 XFDB-3470
Generic Open Relay (non-English advice)	Stop China Spam - Chinese Relay Securing - Japanese Åpne servere – en kilde til uønsket e-post - Norweigan
SMTP AUTH Attacks	SMTP AUTH attacks But my server is secured against relay
SMTP relay behind NAT	How can NAT make me an open relay?
SMTP relay behind proxy	How can an SMTP Proxy Server make me an open relay?
AppleShare Mail Server	AppleShare Mail Server: How To Prevent Unauthorized Mail Relaying
Barracuda Spam Firewall	Barracuda Spam Firewall Mail Relay Restriction Bypassing	CAN-2005-0431 SA-14243
Cobalt RaQ3 Poprelayd	Cobalt RaQ3 Poprelayd Lets Remote Users Relay Mail via SMTP Without Authenticating	CVE-2001-1075 BID-2986 XFDB-6806
Communigate Pro (by Stalker)	Prohibiting Unauthorized Relaying
DataEnter SMTPBeamer	SMTPBeamer – Admin Options – Relay
DMail	DSMTP Relaying_Restrictions
EMWAC IMS	MAPS: EMWAC IMS
Eudora Internet Mail Server (EIMS)	How do I secure my EIMS Server version 2.1 to 3.1 against relaying?
Eudora WorldMail	Securing WorldMail 3 from blacklists Stopping mail relay using the percent % symbol
Exim	Exim HOWTO – Preventing Relaying
Gordano Mail Server	How do I prevent Gordano Products acting as an open relay?
Gordano NTMail 3	NTMail version 3 relay problem	XFDB-2257
IBM VM	MAPS: VM SMTP
Ipswitch IMail	IMail – Mail Relay Options
iSeries AS400	Preventing Third Party Relay Spam on Your iSeries AS400 SMTP Server
Isode Message Switch (M-Switch)	Configuration of M-Switch to Counter Junk E-Mail (Spam)
IT House Mail Server	MAPS: IT House Mail Server
Lotus cc:Mail	MAPS: Lotus cc:Mail
Lotus Domino	How I learned to stop worrying and love the SMTP MTA www-1.ibm.com/support/docview.wss?uid=swg21085603 www-1.ibm.com/support/docview.wss?rs=0&uid=swg21085107	XFDB-6591 CERT-176972
LSMTP	LSMTP: Setting Relay Control
Mac OS X	Mac OS X Server 10.1: How to Set up Restricted SMTP Relay for Apple Mail Mac OS X Server 10.2: How to Prevent Open SMTP Relay
Mad Goat Message Exchange (MX)	MAPS: Message Exchange
MailEnable	MailEnable: What are the best relay settings to use?
Mailtraq	Mailtraq: Preventing Mail Relay Abuse Mailtraq: Relaying Setup
MDaemon	Setting up Relay Control in MDaemon MDaemon Allows Relaying Using Blank Passwords	SA-9520
Mercury Mail	Stop Open Relay in Mercury Mail Programme Configure Mercury Mail to Control SMTP Relay
Messageware MTA	MAPS: Messageware MTA
Microsoft Mail Servers	Microsoft Mail Servers anti-relaying help
MMDF	How to configure MMDF to prevent mail relaying on a per-host basis	XFDB-4343
Netscape Messaging Server	Messaging Server: Anti-Relaying Defenses
Novell Groupwise	Novell Groupwise: How to avoid Relaying or Spamming
M+NetMail (was Novell NetMail)	-
Obtuse	MAPS: Obtuse smtpd
PMDF	PMDF: Preventing SMTP Relaying
PostCast Server	PostCast: Blocking Open Relays
Postfix	Postfix basic relaying configuration
Post.Office	Suggested Anti-Relay Settings for InterMail Post.Office Edition MAPS: Post.Office
QMail	The qmail newbie's guide to relaying
qmail-smtpd-auth	Misconfigured smtp-auth extension to qmail	CVE-2000-0990 BID-1809 XFDB-5382
QuickMail	How do I prevent relaying when using the QuickMail Pro Server?
QuikMail	QwikMail SMTP HELO open relay	CAN-2004-1291 BID-11989 XFDB-18555
Rockliffe Mailsite	Securing Mailsite from blacklists
Sambar	Sambar SMTP server: SMTP Security Sambar Server's SMTP Mail Server May Allow Remote Users to Relay Mail
Sendmail	Sendmail anti-relaying help
SLMail Pro	How do I keep SLMail Pro from being an open relay?
SMail	MAPS: Smail
TenFour TFS Gateway	MAPS: TFS Gateway
TIS SMAP	Patches for smap to reduce e-mail spam and spam relaying
Tobit David	-
Trend Micro InterScan Messaging Security Suite (MSS)	Configuring InterScan MSS
VPOP3	SMTP Relay Protection in VPOP3
WorkgroupMail v6	How to configure your relay settings in WorkgroupMail v6
ZMailer	ZMailer SMTP-server policy filtering rules

Securing Open Relays with Sendmail
Sendmail Version	Advice to Help Secure the Relay	Vulnerability References
SCO Open Server 5.0.5 SCO UnixWare 7.0.0, 7.0.1	SCO Sendmail SMTP anti-relay disabled by default	XFDB-4342
8.8, 8.9-8.12	Relaying Denied/Allowed
8.7, 8.8, 8.9	Putting the Bam-Bam on Spam
8.8	Anti-Spam Provisions in Sendmail 8.8
8.8	Selectively Rejecting Spam Using Sendmail 8.8
8.8	Flexible mail relaying control for Sendmail 8.8
8.9	Configuración del Sendmail 8.9 - Spanish
8.12	Sendmail 8.12 Configurations & Documentation
All	Sendmail Anti-Relaying - Japanese

Securing Open Relays with Microsoft Servers
Exchange Version	Advice to Help Secure the Relay	Vulnerability References
Exchange 5.5	Encapsulated SMTP Address Vulnerability	CVE-1999-0682 BID-567 XFDB-3107
Exchange 5.5	Antirelay configuration in Microsoft Exchange Server 5.5
Exchange 5.5	Relaying and unsolicited commercial e-mail in Exchange Server 5.5
Exchange 5.5 SP1+	Restricting Routing in the Internet Mail Service
Exchange 5.5 SP1+	How to Prevent Mail Relay in Exchange Server 5.5 SP1 or Later
Exchange 5.5 SP1+	Preventing the Internet Mail Service From Relaying Unsolicited Commercial E-Mail Messages
Exchange 5.5 SP2	Is Your Exchange Server Relay-Secure?
Exchange 5.5, 2000	To prevent SMTP relaying with Microsoft Exchange Server
Exchange 5.5, 2000	Controlling SMTP Relaying with Microsoft Exchange
Exchange 5.5, Windows 2000, NT	Authentication Flaw Could Allow Unauthorized Users To Authenticate To SMTP Service	CVE-2002-0054 BID-4205 XFDB-8304 CERT-874115
Windows 2000	Authentication Error in SMTP Service Could Allow Mail Relaying	CVE-2001-0504 XFDB-6803 BID-2988 CERT-435963
Exchange 6.0	Antirelay configuration in Microsoft Exchange Server 6.0
Exchange 2000	Examine Relay Restrictions for Anonymous SMTP Connections in Exchange 2000 Server
Exchange 2003	Examine Relay Restrictions for Anonymous SMTP Connections in Exchange Server 2003
Exchange 2000, Windows SBS	How to block open SMTP relaying and clean up Exchange Server SMTP queues in Windows Small Business Server
Exchange 5.5, 2000, 2003	Guest Account Allows Relaying Regardless of Routing Restrictions
Exchange 2000, 2003	How to troubleshoot mail relay issues in Exchange Server 2003 and in Exchange 2000 Server
All	SMTP relay behavior in Windows 2000, Windows XP, and Exchange Server
All - SMTP AUTH	SMTP AUTH relay attacks Stop Spam From the Inside by Locking Down SMTP

everything you didn't want to have to know about spam

Hosted by spam.abuse.net, with help from Neil Schwartzman. Domain registration by Gregg DesElms. Logo by Art101.

This work is licensed under a Creative Commons License. SPAM is a trademark of Hormel Foods.
Page last updated: 21-May-2007

Securing Open Relays

Securing Open Relays with Sendmail

Securing Open Relays with Microsoft Servers