what does the " No transport provider was available for delivery to this"

[Guest]

What does the error message " No transport provider was
available for delivery to this
recipient." usually indicate? Ive seen this a few times
before, but I have a user who consistently seems to get
this when he replies to an email. We are using a POP3
email service and he is replying to an Exchange server. He
will occasionally get this from POP3 to POP3 as well. Im
wondering what this really means when it says this?

 

[Lanwench [MVP - Exchange]]

I presume he's using a version of Outlook prior to OL2002, and has both POP
and Exchange in the same profile. See Microsoft Knowledgebase article number
245446 for info on the "No transport provider" error message, and a
statement that this is not a supported configuration in prior Outlook
versions....

You can either set up two profiles (awkward), or better still, get rid of
the POP and host your own mail on Exchange with a registered Internet
domain. You're sorta defeating the point of a centralized server by relying
on Outlook to handle Internet mail. Hosting your own domain's mail will be a
lot easier, mail will be faster, you'll be able to use OWA and Out of
Office, you can easily assign multiple addresses to each user, can use
mail-enabled public folders, publicly addressable distribution lists/groups,
and can scan all inbound/outbound mail for viruses using Exchange AV
software on the server.

Please correct me if I've made the wrong assumption about your setup, but it
is the most common cause of this error.