IMAP issue on SBS2008 server

Having an issue with sending e-mails via imap on an SBS 2008 server.  I can login to the account just fine (using outlook 2k7).

I get the following error message when trying to send: "send error 421 4.3.2 service not available closing transmission channel"

Outlook web access and exchange outlook clients work fine.  Imap was working fine 2 or so weeks ago.

Have tried restarting services, etc.

tcsnetworkAsked:
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Michael WorshamStaff Infrastructure ArchitectCommented:
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Rick FeeMessaging Engineer - Disaster Recovery EngineerCommented:
When you attempting to send your using (generally, might be using 587 or others) port 25.   can you telnet to port 25 on the sbs server from that workstation?  

Example:

  Open the      cmd prompt.
Type      telnet server.com 25
Type HELO      server.com
Type MAIL      FROM:you@mydomain.com
You may      get a message saying "250 ok"
Type RCPT      TO:joe@somedomain.com
again, You      may get a message saying "250 ok"
To write      the message, type DATA, followed by your message.
To end the      message, put a period on a new line by itself and press Enter.
Type QUIT      to exit Telnet.
 
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shauncroucherCommented:
Could be a firewall preventing SMTP connection to your Exchange server. Test with telnet and if you get this error straight away I would look for a firewall blocking the port. From the transient failure code you have given, it could well be a firewall that is causing port 25 blocking.

If not then check the settings on the Receive connector. If you are using the Default Connector, this will be listening on port 25 by default and is probably the one you are using.

Check that Exchange Users are allowed to authenticate, and that the server accepts authentication in a form the client will present to it.

Get-ReceiveConnector De* | fl Auth*,Perm* will give you a list of accepted authentication mechanisms and a list of users who can use the connector.

Make sure the email client is set to send authentication credentials to the SMTP Receive connector. If the client is sending Basic authentication, make sure the receive connector is set to allow this (perhaps without TLS if your client does not support TLS).

Shaun
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