Hi
I have tried below code for email validation:

String emailRegex = '^[a-zA-Z0-9_|\\\\#~`=?$^!{}+-]+@[a-zA-Z0-9-]+\\.[a-zA-Z]{2,4}$';

valid email is like sanju.test@test.com should be accetable.
how to write code for below condition
1. Number of characters before @ should be equal or less than 64 characters
2. Below character should NOT be acceptable.
".@"
"@."
3. First and Last character should NOT be "."

Thank you in advance