Abp: SmtpEmailSender error when using gmail

[Goxiaoy]

When I try to use SmtpEmailSender to send an e-mail with html body, then i got an error

[Error] Syntax error, command unrecognized. The server response was: 
System.Net.Mail.SmtpException: Syntax error, command unrecognized. The server response was: 
   at System.Net.Mail.SmtpConnection.ConnectAndHandshakeAsyncResult.End(IAsyncResult result)
   at System.Net.Mail.SmtpTransport.EndGetConnection(IAsyncResult result)
   at System.Net.Mail.SmtpClient.ConnectCallback(IAsyncResult result)

So I have to replace ISmtpEmailSender with my own sender

     context.Services.Replace(
                ServiceDescriptor.Transient<ISmtpEmailSender, MySmtpEmailSender>());

    public class MySmtpEmailSender:SmtpEmailSender
    {

        public MySmtpEmailSender(ISmtpEmailSenderConfiguration smtpConfiguration, IBackgroundJobManager backgroundJobManager) : base(smtpConfiguration, backgroundJobManager)
        {
        }

        protected override async Task SendEmailAsync(MailMessage mail)
        {
            AlternateView textView;
            AlternateView htmlView;
            mail = Fix(mail, out textView, out htmlView);
            try
            {
                using (var smtpClient = await BuildClientAsync())
                {
                    await smtpClient.SendMailAsync(mail);
                }
            }
            catch (Exception e)
            {
                throw;
            }
            finally
            {
                textView?.Dispose();
                htmlView?.Dispose();
                mail.Dispose();
            }

        }

        protected override void SendEmail(MailMessage mail)
        {
            AsyncHelper.RunSync(() => SendEmailAsync(mail));
        }


        protected MailMessage Fix(MailMessage message, out AlternateView textView, out AlternateView htmlView)
        {
            htmlView = null;
            textView = null;
            //force set encoding to utf8
            message.BodyEncoding=Encoding.UTF8;
            if (message.IsBodyHtml)
            {
                var mimeType = new ContentType("text/html");
                htmlView = AlternateView.CreateAlternateViewFromString(message.Body, mimeType);
                message.AlternateViews.Add(htmlView);
            }
            else
            {
                const string mediaType = "text/plain";
                textView = AlternateView.CreateAlternateViewFromString(message.Body, message.BodyEncoding, mediaType);
                textView.TransferEncoding = TransferEncoding.SevenBit;
                message.AlternateViews.Add(textView);
            }
            return message;


        }

So this works for me.

And I notice that MailMessage BodyEncoding will be automatically set after Body set, so part of codes in
EmailSenderBase.cs will never run

[hikalkan]

We'll work on that. Thanks.

[maliming]

@Goxiaoy Can you share your mail settings? For example, host, port, etc.
I can successfully send html mail at other mail service providers, but gmail seems to have problems. The error you mentioned always appears.

[Goxiaoy]

@maliming I replace ISmtpEmailSenderConfiguration so that I can change all the setting definition names and add a new SettingDefinitionProvider to read default value from injection of IOptions<SmtpClientOptions>
So this is my SmtpClientOptions from config file

  "SmtpClient": {
    "Host": "smtp.gmail.com",
    "Port": 587,
    "From": "[email protected]",
    "CredentialsUserName": "[email protected]",
    "CredentialsPassword": "SUPER_STRONG_PASSWORD",
    "EnableSsl": true,
    "UseDefaultCredentials": false 
  }

I live in China which is Internet restricted to gmail but the error metioned happens in my HongKong server before I do those changes.

BTW, is there a convenient way to initial setting values from config file?

[Goxiaoy]

And for anyone who want to use gmail as smtp sender, "Less secure app access" option in your gmail account setting should be turned on . This is gmail stuff but just in case someone get here and looking for help

[maliming]

Our situation is the same (gfw), I can't connect through the proxy.

[Xeevis]

I have this exact same issue with my national provider (EU). I believe the problem is in the underlying SmtpClient implementation because once I switched to MailKit it started working flawlessly with exact same settings.

Abp appears to be using the System.Net.Mail.SmtpClient which is marked as Obsolete and it doesn't support modern protocols.

.

[maliming]

Maybe we can use MailKit directly.

[alexandis]

I have this exact same issue with my national provider (EU). I believe the problem is in the underlying SmtpClient implementation because once I switched to MailKit it started working flawlessly with exact same settings.

Abp appears to be using the System.Net.Mail.SmtpClient which is marked as Obsolete and it doesn't support modern protocols.

.

Is it possible to set default option - "Ignore SSL certificate check" - for MailKit without overriding the class? I need to use some handmade certificate for testing purposes. And now I can't use it for "Forgot password" functionality, where I don't write any code for sending messages at all by myself.

[maliming]

Is it possible to set default option - "Ignore SSL certificate check" - for MailKit without overriding the class?

This is not good practice. Please create a new issue if you are still other question.