def clean_o365_license_list(df):
    """
    This function takes in an Office 365 license list (as a DataFrame) and cleans various aspects and then returns the cleaned list.
    
    Parameters
    ----------
    df : pandas DataFrame

    Returns
    -------
    df : pandas DataFrame
    """
    df['User principal name'] = df['User principal name'].str.lower().str.strip()
    return df