Trying to convert text into email with the help of neighbor cell

Hi everybody, plz help me

i have cells containing email addresses without "at" sign. now I have the website address or domain in the left neighbor cell. I want to use that cell's info to put "at" sign in the right place in the right cell.

example

prioritycargo.com.au nicholasprioritycargo.com.au
publiship.com.au greigrpubliship.com.au
fehlberg.com.au sdfehlbergfehlberg.com.au

also please note that sometimes the value in the left call might not contain the text containing domain. In that case, I want Excel to ignore that.
I hope I have explained it well.

So please advise me a formula or way to do that on entire columns otherwise it will take forever to put manually "at" sign in thousands of cells

Thanks a lot menem for you reply.
Your formula is working great except one error.
In the result, email portion before "at" it is picking up one extra letter from the domain. the domain part on right of "at" sign is complete n ok.

prioritycargo.com.au nicholasprioritycargo.com.au nicholasp"at"prioritycargo.com.au
publiship.com.au greigrpubliship.com.au greigrp"at"publiship.com.au
fehlberg.com.au sdfehlbergfehlberg.com.au sdfehlbergf"at"fehlberg.com.au

Pz check what is causing error

Thnx n Regards

Thanks menem. Now its working like a charm.