ASP.NET MVC Blog Project Email Service Error: ArgumentNullException: Value cannot be null. (Parameter 'host')

ArgumentNullException: Value cannot be null. (Parameter 'host')

I keep getting this error no matter what I do outside of trying to log in it'll give me invalid login attempts and it tells me some usernames are already taken when I try to re-register a user but when I register the user initially it'll give me the null exception.

public async Task SendEmailAsync(string emailTo, string subject, string htmlMessage)
{
        var email = new MimeMessage();

        email.Sender = MailboxAddress.Parse(_mailSettings.Mail);
        email.To.Add(MailboxAddress.Parse(emailTo));
        email.Subject = subject;

        var builder = new BodyBuilder()
        {
            HtmlBody = htmlMessage
        };

        email.Body = builder.ToMessageBody();

        using var smtp = new SmtpClient();
        smtp.Connect(_mailSettings.Host, _mailSettings.Port, SecureSocketOptions.StartTls);
        smtp.Authenticate(_mailSettings.Mail, _mailSettings.Password);

        await smtp.SendAsync(email);

        smtp.Disconnect(true);
}