Hi Darshan,
Put your e-mail validation code in PAI and Use below code, before user_command module.
1.
CHAIN.
field e_MAIL MODULE mod_email_validatie.
ENDCHAIN.
Or.
2 FIELD e_mail MODULE mod_email_validate.
To keep your fields open for input after display an error, always use CHAIN..ENDCHAIN if multiple fields validation and for single Field , write a module based on the FIELD name.
Regards.
Praveer.