Customer Sign Up Issue SMTP - Error

[CaptainFacePalm]

Hello Everybody,

I am running v139h and PHP Version 5.2.6. I have the following mods installed are:
- Capatcha Code
- BOGOF
- Dangling Carrot
- Include & Exclude Tax In Prices
- Mailchimp
- Customer Tax Exempt
- External Polling Sidebox

So I have got that out of the way the issue I am having is when a new customer signs up to our website when they finish creating there account it comes up with Email Error: SMTP Error: The following recipients failed:

What would be causing this to happen I was thinking it might be the Mailchimp add on. But not sure any help would be great also if you can solve this for me I will buy some love sticky yummy doughnuts and coffee. Also I have included and image of what a new customer sees.



Cheers,
Thom

[The_Mech]

Copy your zen cart files back into your FTP, then add each one of your mods individually to identify the cause of the error. There are too many variables in your post.