Delivery is delayed to these recipients or groups

We are trying to email some of our customers and after a long period of time we get an email from OUR exchange server that says Delivery is delayed to these recipients or groups.  

We host our our Exchange 2010 server.  About a week ago we switched our ISPs from Windstream to Time Warner Cable Business Class.  However, we don't filter our outgoing email for spam or anything else.  Why would we all of a sudden be getting these messages from our Exchange server?
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Are you using DNS or a smart host to send your mail?
What does it say under Organization Configuration,Hub Transport, Send Connector
Also,look under tools, queue viewer, sometimes you will get clues there as to why things are sending out.
Is this happening  when sending to any external contact or only some? If only some, check if they are using greylisting.
tholdrenAuthor Commented:
here are the properties of Send Connectorhere are the properties of Send Connectorhere are the properties of Send Connector
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tholdrenAuthor Commented:
This is only happening with one particular customer of ours, which makes it sound like it's greylisting.
Defenitly graylisting. It will take a day or two before they start accepting your emails. Meanwhile you can check the queue to see if emails sent to that domain are still there waiting for retry.
Your send connector looks good and i assume that you have your exchange server name under source server.

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If you want this to be fixed fast, contact their IT personnel and ask them to whitelist your IP.
tholdrenAuthor Commented:
so how do I make sure I'm not greylisted in other places for future purposes?  Is there a global website for checking to see if we're blacklisted/greylisted?
Greyliting has nothing to do with blacklisting. Greylisting is a mechanism that will reject any email coming in the first time, but will accept it the second time. Then it adds the sender IP and email address to a special list which is kept on the server so the next time there is an email coming in from the same ip and the same email address it will be accepted without delay. This is to counterfight the spammers who don't care about retrying, they just send out bunch of emails to bunch of people, whetever goes through goes through. It is a quite effective way to fight spam but it has it's downsides like your case.
Greylisting modifications can be done only by the administrator of that server, because graylisting option is enabled and maintained only on that server. This is unlike the RBL lists that are kept centrally on the net and everyone can use it through DNS lookups.
Your best bet is to contact them and ask then to whitelist you in the greylisting area on their server or appliance.
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