Send gmail from web application hosted on Azure

问题

Newbie to Azure, but got my application successfully published to the cloud as well as my needed database backends (SQL server).

Everything within the application is working as expected except email functionality. I am sending out email alerts via a gmail account, but they do not appear to get sent out. The application does not crash and trying to configure remote debugging has proven difficult.

This is the snippet I am using to send out my emails:

        //Parse html document which will show in outgoing email
        StreamReader reader = new StreamReader(HttpContext.Current.Server.MapPath(ConfigurationManager.AppSettings["template"]));
        string body = reader.ReadToEnd();

        //Populate placeholders with message variables
        body = body.Replace("<%holder%>", value);
        ...Omitted for brevity

        try
        {
            var smtp = new SmtpClient
            {
                Host = "smtp.gmail.com",
                Port = 587,
                EnableSsl = true,
                DeliveryMethod = SmtpDeliveryMethod.Network,
                UseDefaultCredentials = false,
                Credentials = new NetworkCredential(fromAddress.Address, fromPassword)
            };

            using (var message = new MailMessage(fromAddress, toAddress)
            {
                IsBodyHtml = true,
                Subject = subject,
                Body = body,
            })
            {
                smtp.Send(message);
            }
        }

Application didn't crash, so no error message to go off of. So I thought maybe it wasn't able to grab the file in the lines:

StreamReader(HttpContext.Current.Server.MapPath(ConfigurationManager.AppSettings["template"]));
string body = reader.ReadToEnd();

So I tried just sending a hardcoded string as a test:

string body = "test";

Still no email received and no error message to go off of. I'm new to azure web hosting, but is there some configuration I could be missing here? Does Azure allow sending email through third party email clients? Fyi - the above code works against localhost.

回答1:

Sending e-mail from a public cloud is not as trivial as some people believe. There are a lot of things to figure out in order to not get blacklisted. Especially when you intend to use a public mail service.

My first guess is that Azure Data Center IP addresses (or the one you are hosted on) might be blacklisted by mail servers (including Microsoft's very own Office 365).

I have to also mention that recommended way for sending e-mail from an Application hosted in Azure is by using SendGrid. They have a free tier. More information from Microsoft on that subject, can be found here.

The only way to troubleshoot the exact cause of your problem is to contact GMail support and ask them if they block in any way network clients connecting from Azure cloud. Or create a VM in the same Data Center where your web application lives, install some free / trial Mail client, configure it with Google Mail and try to send e-mails. The result most probably will be same as with your application.

来源：https://stackoverflow.com/questions/26881147/send-gmail-from-web-application-hosted-on-azure

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azure

smtp

gmail