Yahoo email compose link not working – compose.mail.yahoo.com

Use email authentication methods, such as SPF, and DKIM to prove that your emails and your domain name belong together, and to prevent spoofing of your domain name. The SPF website includes a wizard to generate the DNS information for your site.

Check your reverse DNS to make sure the IP address of your mail server points to the domain name that you use for sending mail.

Make sure that the IP-address that you're using is not on a blacklist

Make sure that the reply-to address is a valid, existing address.

Use the full, real name of the addressee in the To field, not just the email-address (e.g. "John Smith" <john@blacksmiths-international.com> ).

Monitor your abuse accounts, such as abuse@yourdomain.com and postmaster@yourdomain.com. That means - make sure that these accounts exist, read what's sent to them, and act on complaints.

Finally, make it really easy to unsubscribe. Otherwise, your users will unsubscribe by pressing the spam button, and that will affect your reputation.

That said, getting Hotmail to accept your emails remains a black art.

Be sure to use System.Net.Mail, not the deprecated System.Web.Mail. Doing SSL with System.Web.Mail is a gross mess of hacky extensions.

using System.Net;
using System.Net.Mail;

var fromAddress = new MailAddress("from@gmail.com", "From Name");
var toAddress = new MailAddress("to@example.com", "To Name");
const string fromPassword = "fromPassword";
const string subject = "Subject";
const string body = "Body";

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)
{
    Subject = subject,
    Body = body
})
{
    smtp.Send(message);
}

Additionally go to the Google Account > Security page and look at the Signing in to Google > 2-Step Verification setting.

• If it is enabled, then you have to generate a password allowing .NET to bypass the 2-Step Verification. To do this, click on Signing in to Google > App passwords, select app = Mail, and device = Windows Computer, and finally generate the password. Use the generated password in the fromPassword constant instead of your standard Gmail password.
• If it is disabled, then you have to turn on Less secure app access, which is not recommended! So better enable the 2-Step verification.