I have a small WS'03 based private domain that i'm in the process of building for roll out, however, it's currently in the staging state. The domain build aspects are sound. Internal mail is not currently a priority while downloading mail from ISP mailboxes is. Here are the other givens: Exchange 2007 is hosted by a multi-homed machine (two NIC's) and using an Internet Facing Transport build. I created a 2nd Receive Connector named "mapiLab POP3" that is to receive mail from ISP mailboxes via a 3rd party product (MPC; mapiLab POP3 Connector). MPC is to download this ISP mail and feed Exchange with such; via SMTP. (I posted this issues here as opposed to the 3rd Party forum because i have resolved this to TelNet issue; i think.) The FQDN for the mapiLab POP3 Receive Connector is pop.internaldomain.local. The IP/Port of this connector is 177.177.124.1:19319. This IP is within the local domain's backbone subnet. The connector's RemoteIPRanges {68.142.229.14, 205.178.146.0(255.255.255.0)} are those of the ISP's. I created MX and corresponding A/PTR records to DNS resolve the pop.internaldomain.local host. Priority/Preference is set to 10. DNS maps pop.internaldomain.local and dc0.internaldomain.local to the same IP (i.e. 177.177.124.1). NetStat proves the 19319 port is otherwise unused. nsLookup correctly identifies the MX of pop.internaldomain.local. -I can ping pop.internaldomain.local from any attached node. MPC has a diagnostic utility that checks all (many) aspects of the build and posts status; it fails the SMTP test (421 Service Not Available) while passing all other tests; it even counts the mail in the ISP mail boxes! I TelNet the port configuration as specified for the mapiLab POP3 connector and get the same 421 Service Not Available results; i.e. TelNet>open pop.internaldomain.local 19319. The smtpReceive log posts the following: /timestamp/,0,177.177.124.1:19319,177.177.124.1:10817,+,, /timestamp/,1,177.177.124.1:19319,177.177.124.1:10817,>,"421 4.3.2 Service not available, closing transmission channel", /timestamp/,2,177.177.124.1:19319,177.177.124.1:10817,-,,Local What do i check next? Here is the output from Get-ReceiveConnector: get-receiveconnector|fl Note: internaldomain is substituted name Default DC0 =========== AuthMechanism : BasicAuth Banner : BinaryMimeEnabled : True Bindings : {192.168.0.200:19319} ChunkingEnabled : True DefaultDomain : DeliveryStatusNotificationEnabled : True EightBitMimeEnabled : True DomainSecureEnabled : False EnhancedStatusCodesEnabled : True LongAddressesEnabled : False OrarEnabled : False Fqdn : dc0.internaldomain.local Comment : Enabled : True ConnectionTimeout : 00:10:00 ConnectionInactivityTimeout : 00:05:00 MessageRateLimit : unlimited MaxInboundConnection : 5000 MaxInboundConnectionPerSource : unlimited MaxInboundConnectionPercentagePerSource : 100 MaxHeaderSize : 64KB MaxHopCount : 30 MaxLocalHopCount : 8 MaxLogonFailures : 3 MaxMessageSize : 10MB MaxProtocolErrors : 5 MaxRecipientsPerMessage : 5000 PermissionGroups : ExchangeUsers, ExchangeServers PipeliningEnabled : True ProtocolLoggingLevel : Verbose RemoteIPRanges : {68.94.157.1, 68.94.156.1} RequireEHLODomain : False RequireTLS : False EnableAuthGSSAPI : False Server : DC0 SizeEnabled : EnabledWithoutValue TarpitInterval : 00:00:05 AdminDisplayName : ExchangeVersion : 0.1 (8.0.535.0) Name : Default DC0 DistinguishedName : CN=Default DC0,CN=SMTP Receive Connectors,CN=Protocols,CN=DC0,CN=Servers,CN=Exchange Administrative Group (FYDIBOHF23SPDLT),CN=Administrative Groups,CN=internaldomain Estate,CN=M icrosoft Exchange,CN=Services,CN=Configuration,DC=internaldomain,DC=local Identity : DC0\Default DC0 Guid : 19ade3a4-4917-4eb2-9e73-38177b768e91 ObjectCategory : internaldomain.local/Configuration/Schema/ms-Exch-Smtp-Receive-Connector ObjectClass : {top, msExchSmtpReceiveConnector} WhenChanged : 8/7/2010 12:09:24 PM WhenCreated : 4/7/2009 12:05:01 PM OriginatingServer : dc0.internaldomain.local IsValid : True mapiLab POP3 ============ AuthMechanism : BasicAuth Banner : BinaryMimeEnabled : True Bindings : {177.177.124.1:19319} ChunkingEnabled : True DefaultDomain : DeliveryStatusNotificationEnabled : True EightBitMimeEnabled : True DomainSecureEnabled : False EnhancedStatusCodesEnabled : True LongAddressesEnabled : False OrarEnabled : False Fqdn : pop.internaldomain.local Comment : Enabled : True ConnectionTimeout : 00:10:00 ConnectionInactivityTimeout : 00:05:00 MessageRateLimit : unlimited MaxInboundConnection : 5000 MaxInboundConnectionPerSource : 20 MaxInboundConnectionPercentagePerSource : 2 MaxHeaderSize : 64KB MaxHopCount : 30 MaxLocalHopCount : 8 MaxLogonFailures : 3 MaxMessageSize : 10MB MaxProtocolErrors : 5 MaxRecipientsPerMessage : 200 PermissionGroups : AnonymousUsers PipeliningEnabled : True ProtocolLoggingLevel : Verbose RemoteIPRanges : {68.142.229.14, 205.178.146.0(255.255.255.0)} RequireEHLODomain : False RequireTLS : False EnableAuthGSSAPI : False Server : DC0 SizeEnabled : Enabled TarpitInterval : 00:00:05 AdminDisplayName : ExchangeVersion : 0.1 (8.0.535.0) Name : mapiLab POP3 DistinguishedName : CN=mapiLab POP3,CN=SMTP Receive Connectors,CN=Protocols,CN=DC0,CN=Servers,CN=Exchange Administrative Group (FYDIBOHF23SPDLT),CN=Administrative Groups,CN=internaldomain Estate,CN= Microsoft Exchange,CN=Services,CN=Configuration,DC=internaldomain,DC=local Identity : DC0\mapiLab POP3 Guid : 41bb0785-9aad-415d-8c25-c923042881f4 ObjectCategory : internaldomain.local/Configuration/Schema/ms-Exch-Smtp-Receive-Connector ObjectClass : {top, msExchSmtpReceiveConnector} WhenChanged : 8/9/2010 12:09:47 AM WhenCreated : 8/2/2010 11:27:04 PM OriginatingServer : dc0.internaldomain.local IsValid : True ThanksGlenn of xSyLent

For those curious: I specified the local IP's (multi-homed) of the Hub Transport host for the subject Receive Connector; this is also a requisite for the MPC product as it's installed on the same host. Rebooted. It works now. There were a few other Exchange issues that also got resolved but i don't believe they're related. I believe the problem was the original IP spec for RemoteIPranges; e.g. The TelNet session had to be initiated from a host that was within the bounds of the RemoteIPranges spec. Coincidentally, this is where MPC was also hosted! Glenn of xSyLent

It was my pleasure! Cheers!Glenn of xSyLent