Dont know where to look

I know very little about asp and sql server and IIS. However, several problems, mostly with emailing, have popped up unexpectedly. I don't know what/where to look, so I'll start this post in this forum. Please let me know if I need to move it.

In the past week, the emailing functionality has just stopped working. You can navigate through the remaining pages fine though. There is an .asp page that you can send an email, looks very basic. When you click send, you are redirected to a page with the following error:
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Server object error 'ASP 0177 : 800401f3'
Server.CreateObject Failed
/SendMail.asp, line 18
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Here is line 18:
Set CDOSession = Server.CreateObject("MAPI.Session")

Either coincidently or not, when the IP address of our exchange server was changed, this stopped working. It does look like our exchange server is referenced in this .asp file by 'name' rather than 'hardcoded' IP.

Can anyone shed some light on this issue?

Thank you!
-Tim