ArgumentNullException for address when sending email using NetCore.MailKit

Question

I am using NetCore.MailKit NuGet package to help me send an email which contains a link to confirm their email when the user registers. I have followed the steps on their Github page but, I am getting an ArgumentNullException for the address, even though I have set the sending address.

The error:

ArgumentNullException: Value cannot be null. (Parameter 'address')
    MimeKit.MailboxAddress..ctor(Encoding encoding, string name, string address)

The above error occurs when is send the email in my controller using IEmailService:

_EmailService.Send("usersemail@gmail.com", "subject", "message body");

This is my appsettings.json configuration:

  "EmailConfiguration": {
    "Server": "smtp.gmail.com",
    "Port": 587,
    "SenderName": "name",
    "SenderEmail": "mygmail@gmail.com",
    "SenderPassword": "My gmail password"
  }

This is my setup in startup.cs

    services.AddMailKit(optionBuilder =>
    {
        optionBuilder.UseMailKit(new MailKitOptions()
        {
            //get options from sercets.json
            Server = Configuration["Server"],
            Port = Convert.ToInt32(Configuration["Port"]),
            SenderName = Configuration["SenderName"],
            SenderEmail = Configuration["SenderEmail"],
            Account = Configuration["SenderEmail"],
            Password = Configuration["SenderPassword"],
            Security = true
        });
    });

Below is the code for EmailService:

    public void Send(string mailTo, string subject, string message, bool isHtml = false)
    {
        SendEmail(mailTo, null, null, subject, message, Encoding.UTF8, isHtml);
    }

    private void SendEmail(string mailTo, string mailCc, string mailBcc, string subject, string message, Encoding encoding, bool isHtml)
    {
        var _to = new string[0];
        var _cc = new string[0];
        var _bcc = new string[0];
        if (!string.IsNullOrEmpty(mailTo))
            _to = mailTo.Split(',').Select(x => x.Trim()).ToArray();
        if (!string.IsNullOrEmpty(mailCc))
            _cc = mailCc.Split(',').Select(x => x.Trim()).ToArray();
        if (!string.IsNullOrEmpty(mailBcc))
            _bcc = mailBcc.Split(',').Select(x => x.Trim()).ToArray();

        Check.Argument.IsNotEmpty(_to, nameof(mailTo));
        Check.Argument.IsNotEmpty(message, nameof(message));

        var mimeMessage = new MimeMessage();

        //add mail from
        mimeMessage.From.Add(new MailboxAddress(_MailKitProvider.Options.SenderName, _MailKitProvider.Options.SenderEmail));

        //add mail to 
        foreach (var to in _to)
        {
            mimeMessage.To.Add(MailboxAddress.Parse(to));
        }

        //add mail cc
        foreach (var cc in _cc)
        {
            mimeMessage.Cc.Add(MailboxAddress.Parse(cc));
        }

        //add mail bcc 
        foreach (var bcc in _bcc)
        {
            mimeMessage.Bcc.Add(MailboxAddress.Parse(bcc));
        }

        //add subject
        mimeMessage.Subject = subject;

        //add email body
        TextPart body = null;

        if (isHtml)
        {

            body = new TextPart(TextFormat.Html);
        }
        else
        {
            body = new TextPart(TextFormat.Text);
        }
        //set email encoding
        body.SetText(encoding, message);

        //set email body
        mimeMessage.Body = body;

        using (var client = _MailKitProvider.SmtpClient)
        {
            client.Send(mimeMessage);
        }
    }

As you can see I have set everything, am I missing something here? why is address null at MimeKit.MailboxAddress()?

I have updated the question with EmailService, the rest can be found at the link I provided @JSteward — KB_Shayan, Jan 31 '20 at 21:57
_EmailService.Send("usersemail@gmail.com", "subject", "message body"); @jstedfast — KB_Shayan, Jan 31 '20 at 22:02
No, it gets thrown inside the EmailService.SendEmail() method - but where? — jstedfast, Jan 31 '20 at 22:03
When MailBoxAddress instance is created, it says the address is null @jstedfast — KB_Shayan, Jan 31 '20 at 22:13
Is it this line? `mimeMessage.From.Add(new MailboxAddress(_MailKitProvider.Options.SenderName, _MailKitProvider.Options.SenderEmail));` — jstedfast, Jan 31 '20 at 22:13

score 3 · Accepted Answer · answered Jan 31 '20 at 22:14

You seem to be not loading your configuration settings correctly. I suspect the failing line in your code is

//add mail from
mimeMessage.From.Add(new MailboxAddress(_MailKitProvider.Options.SenderName, _MailKitProvider.Options.SenderEmail));

The Options are all null, which causes the exception.

When you load the settings from a configuration file you need to prepend the section name to the variables. E.G.

services.AddMailKit(optionBuilder =>
{
    optionBuilder.UseMailKit(new MailKitOptions()
    {
        //get options from sercets.json
        Server = Configuration["EmailConfiguration:Server"],
        Port = Convert.ToInt32(Configuration["EmailConfiguration:Port"]),
        SenderName = Configuration["EmailConfiguration:SenderName"],
        SenderEmail = Configuration["EmailConfiguration:SenderEmail"],
        Account = Configuration["EmailConfiguration:SenderEmail"],
        Password = Configuration["EmailConfiguration:SenderPassword"],
        Security = true
    });
});

score 0 · Answer 2 · answered Jan 31 '20 at 22:13

My guess is that the exception is being thrown on the following line:

mimeMessage.From.Add(new MailboxAddress(_MailKitProvider.Options.SenderName, _MailKitProvider.Options.SenderEmail));

This means that _MailKitProvider.Options.SenderEmail is null.

I know you expect these values to be loaded correctly from your appsettings.json file, but seemingly, they are not being loaded for some reason.

ArgumentNullException for address when sending email using NetCore.MailKit

2 Answers2