I'm working in ASP.NET Core and using MailKit for email functionality. The method I've previously used is no longer working.
I have an SmtpOptions.cs class:
public class SmtpOptions
{
public string Server { get; set; } = "smtp.gmail.com"; //Gmail limited to 2000 emails per day
public int Port { get; set; } = 465; //default for SSL using GMail
public string User { get; set; } = "myEmail@gmail.com"; //must match server domain
public string Password { get; set; } = "myPwd";
public bool UseSsl { get; set; } = true; //gmail requires SSL
public bool RequiresAuthentication { get; set; } = true; //gmail requires authentication
public string PreferredEncoding { get; set; } = string.Empty;
}
and EmailSender.cs class:
public class EmailSender
{
public EmailSender()
{
}
public async Task SendEmailAsync(
SmtpOptions smtpOptions,
string to,
string from,
string subject,
string plainTextMessage,
string htmlMessage,
string replyTo = null)
{
if (string.IsNullOrWhiteSpace(to))
{
throw new ArgumentException("no to address provided");
}
if (string.IsNullOrWhiteSpace(from))
{
throw new ArgumentException("no from address provided");
}
if (string.IsNullOrWhiteSpace(subject))
{
throw new ArgumentException("no subject provided");
}
var hasPlainText = !string.IsNullOrWhiteSpace(plainTextMessage);
var hasHtml = !string.IsNullOrWhiteSpace(htmlMessage);
if (!hasPlainText && !hasHtml)
{
throw new ArgumentException("no message provided");
}
var m = new MimeMessage();
m.From.Add(new MailboxAddress("", from));
if (!string.IsNullOrWhiteSpace(replyTo))
{
m.ReplyTo.Add(new MailboxAddress("", replyTo));
}
m.To.Add(new MailboxAddress("", to));
m.Subject = subject;
//m.Importance = MessageImportance.Normal;
//Header h = new Header(HeaderId.Precedence, "Bulk");
//m.Headers.Add()
BodyBuilder bodyBuilder = new BodyBuilder();
if (hasPlainText)
{
bodyBuilder.TextBody = plainTextMessage;
}
if (hasHtml)
{
bodyBuilder.HtmlBody = htmlMessage;
}
m.Body = bodyBuilder.ToMessageBody();
using (var client = new SmtpClient())
{
await client.ConnectAsync(
smtpOptions.Server,
smtpOptions.Port,
smtpOptions.UseSsl)
.ConfigureAwait(false);
// Note: since we don't have an OAuth2 token, disable
// the XOAUTH2 authentication mechanism.
client.AuthenticationMechanisms.Remove("XOAUTH2");
// Note: only needed if the SMTP server requires authentication
if (smtpOptions.RequiresAuthentication)
{
await client.AuthenticateAsync(smtpOptions.User, smtpOptions.Password)
.ConfigureAwait(false);
}
await client.SendAsync(m).ConfigureAwait(false);
await client.DisconnectAsync(true).ConfigureAwait(false);
}
}
public async Task SendMultipleEmailAsync(
SmtpOptions smtpOptions,
string toCsv,
string from,
string subject,
string plainTextMessage,
string htmlMessage)
{
if (string.IsNullOrWhiteSpace(toCsv))
{
throw new ArgumentException("no to addresses provided");
}
if (string.IsNullOrWhiteSpace(from))
{
throw new ArgumentException("no from address provided");
}
if (string.IsNullOrWhiteSpace(subject))
{
throw new ArgumentException("no subject provided");
}
var hasPlainText = !string.IsNullOrWhiteSpace(plainTextMessage);
var hasHtml = !string.IsNullOrWhiteSpace(htmlMessage);
if (!hasPlainText && !hasHtml)
{
throw new ArgumentException("no message provided");
}
var m = new MimeMessage();
m.From.Add(new MailboxAddress("", from));
string[] adrs = toCsv.Split(',');
foreach (string item in adrs)
{
if (!string.IsNullOrEmpty(item)) { m.To.Add(new MailboxAddress("", item)); ; }
}
m.Subject = subject;
m.Importance = MessageImportance.High;
BodyBuilder bodyBuilder = new BodyBuilder();
if (hasPlainText)
{
bodyBuilder.TextBody = plainTextMessage;
}
if (hasHtml)
{
bodyBuilder.HtmlBody = htmlMessage;
}
m.Body = bodyBuilder.ToMessageBody();
using (var client = new SmtpClient())
{
await client.ConnectAsync(
smtpOptions.Server,
smtpOptions.Port,
smtpOptions.UseSsl).ConfigureAwait(false);
// Note: since we don't have an OAuth2 token, disable
// the XOAUTH2 authentication mechanism.
client.AuthenticationMechanisms.Remove("XOAUTH2");
// Note: only needed if the SMTP server requires authentication
if (smtpOptions.RequiresAuthentication)
{
await client.AuthenticateAsync(
smtpOptions.User,
smtpOptions.Password).ConfigureAwait(false);
}
await client.SendAsync(m).ConfigureAwait(false);
await client.DisconnectAsync(true).ConfigureAwait(false);
}
}
}
That are used in a function call:
public async void ContactMessage(string title, string message, string toEmail)
{
string thisMessage = "No Message Provided";
if (!String.IsNullOrEmpty(message)) { thisMessage = message; } //in case empty form
string thisTitle = title;
//create email objects
EmailSender emailSender = new EmailSender();
SmtpOptions smtpOptions = new SmtpOptions(); //default settings ok
string fromEmail = smtpOptions.User;
string subjectLine = "Message Title";
await emailSender.SendEmailAsync(smtpOptions, toEmail, fromEmail, subjectLine, thisMessage, "");
}
As stated, this method has worked before but now I'm getting a failure of Gmail to respond. I've checked and have IMAP and POP enabled.
The specific exception reads: "System.Net.Internals.SocketExceptionFactory.ExtendedSocketException: 'A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond'"
This code has not been deployed but causes this error in the test environment. Moving to a differently firewalled system causes the error "Mailkit.Security.Authentication; MailKit authentication is too weak"
Testing with Yahoo! smtp allows the above code to work so it seems like the compatibility between Mailkit and Gmail has changed. What is the appropriate Mailkit configuration for using Gmail?
