Changing Cells in List that ends with certain text

I have a list of email address (~5797). Many of the email address are incomplete. The email address ends with ".c" or ".co" instead of ".com" This is the same for .net as well. However, all of the email addresses are unique by either there account name or domain name. Example: AndrewTest@Example.com. "AndrewTest" = account, and "Example.com" = domain. Does anyone know of a formula to do this automatically without me going through each individual one and changing it manually? I am not sure if there is an "IF" or "replace" formula to accomplish this.

Thanks.

Maybe samething like this?

Pls check the file

Azumi

ie data at A1 so try this
=LEFT(A1,FIND(".",A2,LEN(A1)-4))&INDEX({"com","com","net"},MATCH(REPLACE(A1,1,FIND(".",A2,LEN(A1)-4),),{"co","c","n"},0))

Azumi,
Your workbook helped. Thank you. Is there a way just replace the cell instead of populating it into the cell to the right? I would prefer not to have to move and replace every cell manually. Secondly, if I had an email address without a "com" of "net" (ie. andrew@test.) is there a way to auto populate a "com".

Thanks.
Andrew