CSV formula/macros

I have several excel spreadsheets that have different column formats. However they all have an email column with email addresses. Next to the email column there is an email format column. I would like a script that would read from the email column and then add in the email format column a string of characters that will explain how the email is construed. For example if the email says [login to view URL]@[login to view URL] then the email format column will show _F_._L_@_D_ _F_ being FIRST NAME _L_ being LAST NAME _D_ being domain some email addresses have other formats. For example it could be bmarkey@xyz so the email format will be _FF__L_@_D_ _FF_ being first letter of the first name _FL_ first letter of the last name sometimes it can also be just _F_@_D_ or _L_@_D_ Also the separators between names can be a . (dot) but also an _ (underscore) like in bob_markey@[login to view URL] which becomes _F___L_@_D_ I would like the end result to be a formula or anything that I can simply plug into all my different CSV sheets. MAX BID: $10