I've encountered some problems sending to some (Comcast and Google) domains since the change to make IPv6 preferred. My ISP does not provide IPv6 internet service. While I have fixed the transport problems (via an ISATAP tunnel), all is not yet well.
I am now receiving an email notification indicating: No SMTP server defined. Use real server address instead of 127.0.0.1 in your account.
I have confirmed from the Exchange Protocol logs that the SMTP session has been established to the indicated IPv6 address for the destination mail server. The error message originates from that end. I also notice that my send address is ::1 in the log, and
that it is 127.0.0.1 for logged IPv4 traffic.
I have read that Comcast and Google are doing sender address verification for IPv6 addresses. I can attest that verification is not performed for IPv4 addresses, since I am able to send.
Here are the problems:
1) The Prefer IPv4 EasyFix and registry setting appears to do nothing on Server 2008 R2. Exchange 2010 is consistently selecting the IPv6 destination address after looking up the mail servers.
2) I can find no way to configure the Send Connector address on Exchange 2010. I can find no references to the loopback interface with the Exchange Management console. I do find a reference to a 'SourceIPaddress' using the Get-SendConnector shell command,
but the documentation indicates (and I have verified that) it is only used on Edge Servers and ignored on the Transport server. This is a Small Business Server (Everything is on one machine; it sends from the Transport Server.), so the loopback would be one
path to the Send Connector.
Can anyone provide information on how my Send Connector (or the sender address in the SMTP stream) address is currently and may be configured for Exchange Server 2010?
I have also noticed that the netsh interface dns show state displays a parameterResolution Query Behavior with value 'Resolve only IPv6 addresses for names'. I assume that this parameter would show up underdnscache in the registry, but since the parameter is defaulted (and is not present) I have no idea how it is named and can find no indication what it really does. Am hoping that this might be a substitute for thePrefer IPv4 registry setting since I only need to keep Exchange from translating destinations to IPv6. Any thoughts? Seems better than disabling IPv6 altogether.