Unble to send via IMAP


We currently have an Exchange 2003 server and have a few users on MAC using Windows Mail with their accounts setup as IMAP accounts.

This was working fine but had an issue where someone used the server as a relay and was blocked by our antispam provider - Messagelabs. We then locked down the server to allow just the messagelabs IP addresses on the server.

How ever I am now not able to send emails via IMAP but I can receive emails. This is the same on Outlook too so its not just a MAC issue.

I have a user account set up on my Outlook and get the following send\receive error - Sending reported error (0x800CCC0F) : The connection to the server was interrupted. If this problem continues, contact your server administrator or internet service provider.

The firewall has the IMAP port open as I am able to receive just not send.

Is there anything I need to set up on exchange to be able to send using IMAP and not leave the server open for replay from unauthenticated users?

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Simon Butler (Sembee)ConsultantCommented:
You don't send via IMAP.
IMAP is a protocol for reading email on the server, has nothing to do with delivery.
The problem is that you have locked down the SMTP server to the Message Labs IP range.
You have two options.

1. Change the IP range to include the addresses of the MAC clients.
2. Adjust the settings to allow relaying. Then configure the users who need to relay - specifically excluding the administrator account. Then in the Mac clients, configure them to authenticate when sending.

Obviously the best option would be to upgrade to a more recent version of Exchange, which will allow the Mac clients to connect via EWS.

granite03Author Commented:
Thanks Simon,

I know how IMAP and SMTP work, it just came out wrong in my description :)

I have added my external IP address to the IP list along with the Messagelabs IPs and also allowed my user account to authenticate although all authenticated users are set to be able to send anyway but I am still unable to send.

They are going to be moving to O365 soon but until then I need to get them working again.


Is there anything else I can check.
granite03Author Commented:
Sorry also forgot to mention I have this issue even when sending emails when users are in the office on the same network as the exchange server.

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Simon Butler (Sembee)ConsultantCommented:
Is the client setup to authentication?
That has to be specific credentials, not "same as incoming" or something like that.
For SMTP the format is usually domain\username and then the password.

Generally speaking for clients sending mail you want them to use the submission port (587) rather than the "normal" smtp port (25).  It's possible that your clients are actually defaulting to using that port anyway, in which case you would want to make sure that exchange is configured to receive on that port.

To troubleshoot this, go to a client that is experiencing the problem; first verify which port it is using to send to.  Then try to telnet to that port from the client.  If you can't get a connection at all, then given what you said about it not working even when on network, the chances are that exchange is not listening on the right port (which is unlikely if the client is using 25).  Otherwise look for a firewall in the path between you and the server.

If you can get a connection, try simulating sending an email with the SMTP protocol, and see at what point it breaks down.  Eg
<- 220
-> HELO me
<- 2xx
-> MAIL FROM:<me@mydomain.com>
<- 2xx
-> RCPT TO:<you@somewhere.else>
<- ???

My guess is that somewhere in that conversation you are going to get "5xx some kind of error message", which will hopefully identify what the problem is.  That will tell you for example whether or not authentication is required.  If it is, unfortunately that is quite hard to do by hand, but at least you will know that everything is working up to that point.

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granite03Author Commented:

Ok I have finally had a chance to work on this again.

I am not able to carryout a successful test of the account settings from my machine outside the network.

That is about as far as it gets, when I try to send an email from the imap account to my email address I get a undeliverable with the error below:

Your message did not reach some or all of the intended recipients.

      Subject:      RE: Test
      Sent:      09/06/2015 16:06

The following recipient(s) cannot be reached:

      My name on 09/06/2015 16:06
            Server error: '550 5.7.1 Unable to relay for my external email address'

granite03Author Commented:
sorry I meant:

I am now able to carryout a successful test of the account settings from my machine outside the network.
OK so it sounds like Simon's comments were on the money.  You need to make sure (a) that your server is configured to allow authenticated users to relay, and (b) that your clients are configured to actually do the authentication (unlike HTTP,  SMTP doesn't prompt to authenticate, the client has to explicitly initiate it).  My guess is that (a) is already good, but check.  For (b), on the client go to the SMTP server settings and configure a user name and password.  Depending on the client you may need to also select something like "My server requires authentication", and you may or may not be able to simply select "use same credentials as for IMAP" or similar.  The critical point is that you must explicitly enable authentication on the SMTP settings - anything you have set for IMAP will not carry through automatically to SMTP unless you tell it to.

You said above your users are using Windows Mail on Mac - I'm guessing what you meant was they are using Mac Mail on Mac :-).  In which case it should just be a question of explicitly setting username and password on the SMTP server settings.
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