Email identificatin procedure

How do we configure a Person’s email id from his name?

Example
Name: Paul Clark

email option 1 : paul.clark@email.com
option 2 : paul_clark@email.com
option 3 : paulclark@email.com

As one can see the differnces between the three which procedure must be adopted by any organisation as an efficient one.

If I remember correctly when yahoo was giving us an email option it did not have option 1.

Under option 2 the “_” is camafloged in any word document as it changes by a complete underline.

&
Option 3 makes the id very big.

Please let me know your comments on this

Dr.A.S.Prakash