def normalize_email(email):
    """
    Email Address Normalization.

    1. Remove leading and trailing spaces.
    2. Convert all ASCII characters to lowercase.
    3. In gmail.com email addresses, remove the following characters from the username part of the email address:
      1) The period (. (ASCII code 46)).
         For example, normalize jane.doe@gmail.com to janedoe@gmail.com.
      2) The plus sign (+ (ASCII code 43)) and all subsequent characters.
         For example, normalize janedoe+home@gmail.com to janedoe@gmail.com.
    """
    email = email.strip().lower()
    (user, domain) = email.split("@")
    if domain == "gmail.com":
        user = user.replace(".", "").split("+")[0]
        email = "@".join((user, domain))
    return email