Develop Reference

Send email from .NET Core using Microsoft 365 Family subscription

I have an Office 365 Family subscription (thus using outlook.com) and are trying to send email from a C# application I'm working on. Does anybody know if this is even possible?
From my research there seems to be a lot of people having issue with this approach but I'm trying hard to find out if it's supported

There are different ways of doing the required job:
Use standard .net mechanisms, the same question was posted here:
using (SmtpClient client = new SmtpClient()
{
Host = "smtp.office365.com",
Port = 587,
UseDefaultCredentials = false, // This require to be before setting Credentials property
DeliveryMethod = SmtpDeliveryMethod.Network,
Credentials = new NetworkCredential("alias#fulldomain.com", "password"), // you must give a full email address for authentication
TargetName = "STARTTLS/smtp.office365.com", // Set to avoid MustIssueStartTlsFirst exception
EnableSsl = true // Set to avoid secure connection exception
})
{
MailMessage message = new MailMessage()
{
From = new MailAddress("alias#fulldomain.com"), // sender must be a full email address
Subject = subject,
IsBodyHtml = true,
Body = "<h1>Hello World</h1>",
BodyEncoding = System.Text.Encoding.UTF8,
SubjectEncoding = System.Text.Encoding.UTF8,
};
var toAddresses = recipients.Split(',');
foreach (var to in toAddresses)
{
message.To.Add(to.Trim());
}
try
{
client.Send(message);
}
catch (Exception ex)
{
Debug.WriteLine(ex.Message);
}
}
The SmtpClient is usable in .NET Core, but its use isn't recommended. Instead, consider using https://github.com/jstedfast/MailKit .
Use Graph API.

And for anybody else having problems with using smtp.office365.com and sending email through code. You need to add an "app password" in your Microsoft Account. The regular password you use to login to outlook.com will not work

SMTP server requires a secure connection - gmail

I am running an ASP.Net application on windows azure and I need to send an email from it. I am trying to send it using my gmail account as follows, however when I attempt to send it, I get the following error:
The SMTP server requires a secure connection or the client was not
authenticated. The server response was: 5.5.1 Authentication Required.
Learn more at
The code:
private static readonly string EMAIL_ADDRESS = "mymail#gmail.com";
private static readonly string EMAIL_FROM = "MY FROM NAME";
private static readonly string EMAIL_PASS = "my Password";
private static readonly string EMAIL_HOST = "smtp.gmail.com";
private static readonly int EMAIL_PORT = 587;
private static readonly bool EMAIL_SSL = true;
private static readonly SmtpDeliveryMethod EMAIL_DELIVERY_METHOD = SmtpDeliveryMethod.Network;
private static readonly bool EMAIL_DEFAULT_CREDENTIALS = false;
public static void SendEmail(string recipientEmail, string subject, string body) {
var fromAddress = new MailAddress(EMAIL_ADDRESS, EMAIL_FROM);
var toAddress = new MailAddress(recipientEmail, "MY CLIENT NAME");
var smtp = new SmtpClient {
Host = EMAIL_HOST,
Port = EMAIL_PORT,
EnableSsl = EMAIL_SSL,
DeliveryMethod = EMAIL_DELIVERY_METHOD,
UseDefaultCredentials = EMAIL_DEFAULT_CREDENTIALS,
Credentials = new NetworkCredential(fromAddress.Address, EMAIL_PASS,EMAIL_HOST)
};
using (var message = new MailMessage(fromAddress, toAddress) {
Subject = subject,
Body = body,
Priority = MailPriority.High
}) {
smtp.Send(message);
}
}
I have enabled Less Secure Sign-in, and the configuration seems to be fine. What is the problem?

Try to remove the UseDefaultCredentials property.
If that doesn't work, set the properties individually (not using the object initialiser) and make sure Credentials is set after UseDefaultCredentials
see c# SmtpClient class not able to send email using gmail

I know this answere is a bit late, but You are using a NOT SECURE WAY to login to your gmail. Gmail actually throws an error but this is not send to you. You may receive an email that says something like:
Someone tried to connect to you gmail account from an unsecure
application
Or some similar. In this case you have to visit
https://www.google.com/settings/security/lesssecureapps
(Provided you are logged in)
and set this option to allow unsecure apps. Than you are allowed to send mails (even in this unsecure way).
Having the same problem atm but I dont want to allow unsecure apps, I want to change my code to be secure. But cant find anything that solves this.

Your code looks fine. Did you check that the email address hasn't been locked out? I.e. actually login to that email account on your browser. It happened to me before where the gmail account I was using got locked.

smtpclient is not initiating smtp traffic

We have two versions of a web application running in IIS 7.5 on Windows Server 2008R2, with almost identical running conditions. Both versions are using the same set of email code to relay smtp messages to an internal Exchange2010 server. The first application completes the request, and sends the email without a hitch. However, the second, which uses a custom security model (being the only major difference between the apps), will not even initiate an smtp request at all. There is code to handle exceptions from SMTPClient.send, but none are occurring. Both versions send mail from development machine running with visual studio application server.
Wireshark shows complete request and verification of credentials for application one, but no traffic is detected at all from application two. The virtual running the IIS instance has it's IP address accepted by the Exchange server, and is on the same domain etc. The firewall is turned off for the domain.
UseDefaultCredentials is being implemented for authentication of smtp messages. Each application is running inside a separate app pool, but are using the same user (NetworkService) and have identical security permissions on the wwwroot etc.
Any insight is appreciated as to why the one application is seemingly doing nothing when using .Net Mail.SMTPClient on the IIS 7.5 server.
Code in a nutshell is as follows (ignore possible method signature mismatches, code is in different classes, default SMTP host is defined by Email.Host)
protected void taskHeaderGrid_OnItemCommand(object sender, GridCommandEventArgs e)
{
try {
Int32 recordsAcivated = workFlowController.activateWorkFlow((IDbConnection)myConn, null, System.Convert.ToInt32(taskHdrIdTxt));
}
catch (Exception) {
AddMessage(Message.eMessageType.Error, "Warning: email message to alert users that next task has been activated was not sent.");
}
}
public Int32 activateWorkFlow(IDbConnection currConnection, IDbTransaction currTran, Int32 workFlowId)
{
//Send out the mails......
if (!string.IsNullOrWhiteSpace(primaryPersonEmail))
{
emailController.sendMessage(primaryPersonEmail, "Task has been activated.", string.Format("Hdr:({0}) Detail:({1})", taskHeaderDTO.Description, jobFunctionDTO.JobDescription));
}
if (!string.IsNullOrWhiteSpace(secondaryPersonEmail))
{
emailController.sendMessage(secondaryPersonEmail, "Task has been activated.", string.Format("Hdr:({0}) Detail:({1})", taskHeaderDTO.Description, jobFunctionDTO.JobDescription));
}
}
public void sendMessage(string toEmailAddr, string txtmessage, string subject)
{
Email.Host = hostName;
Email.Send(subject, txtmessage, senderEmailAddr, toEmailAddr);
}
public static void Send(string subject, string body, string from, IEnumerable<string> to, string smtphost)
{
Send(CreateMessage(subject, body, from, to), smtphost);
}
public static void Send(System.Net.Mail.MailMessage msg, string smtphost)
{
using (System.Net.Mail.SmtpClient client = new System.Net.Mail.SmtpClient(smtphost))
{
if (InterceptEmails == true)
{
ApplyFailSafe(msg);
}
client.UseDefaultCredentials = true;
client.Send(msg);
}
}
public static System.Net.Mail.MailMessage CreateMessage(string subject, string body, string from, IEnumerable<string> to, IEnumerable<string> cc, IEnumerable<string> bcc)
{
System.Net.Mail.MailMessage msg = new System.Net.Mail.MailMessage();
msg.Subject = subject;
msg.Body = body;
msg.From = new System.Net.Mail.MailAddress(from);
msg.IsBodyHtml = true;
if (to != null)
{
foreach (string email in to)
msg.To.Add(email);
}
if (cc != null)
{
foreach (string email in cc)
msg.CC.Add(email);
}
if (bcc != null)
{
foreach (string email in bcc)
msg.Bcc.Add(email);
}
return msg;
}

I've created an example method for you, that will attempt to send an e-mail. Here are a couple of items to note about the implementation:
Settings Class - It holds all of our Client / Server data. Which helps keep the code decoupled for re-usability.
public static void SendNotificationEmail(Settings setting)
{
// Loop through our generic list.
foreach(string email in setting.To)
{
// Assign our email parameters to the message.
MailMessage message = new MailMessage(setting.From, email, setting.Subject, setting.Body);
//Build Our Smtp Client
SmtpClient client = new SmtpClient();
client.Host = setting.SmtpServer;
client.Port = setting.Port;
client.Timeout = setting.Timeout;
client.DeliveryMethod = SmtpDeliveryMethod.Network;
client.UseDefaultCredentials = false;
client.Credentials = new NetworkCredential(setting.Username, setting.Password);
}
}
In order to truly help you we would need that Security Model and the precise code that is giving you trouble. Hopefully my implementation might contain a missing piece. This works on my server running the latest version of Internet Information System (IIS).
Also SMTP may fail silently without valid credentials.

Issue was resolved, a higher level configuration and error before the SMTP email was being generated caused the issue.

System.Net.Mail.SmtpException: The SMTP server requires a secure connection or the client was not authenticated

I'm trying to send email with my website's address from a C# application.
This worked fine for several months until recently. (maybe my provider changes some things or someone else changed settings)
Here's the code:
private void sendEmail(Email invite) {
MailMessage mail = new MailMessage();
SmtpClient SmtpServer = new SmtpClient(smtpServerName);
mail.From = new MailAddress(emailUsername);
mail.To.Add(invite.RecipientEmail);
mail.Subject = invite.MessageSubject;
mail.Body = invite.MessageBody;
SmtpServer.UseDefaultCredentials = false;
SmtpServer.Port = 587;
SmtpServer.Credentials = new System.Net.NetworkCredential(emailUsername, emailPassword);
// SmtpServer.EnableSsl = true;
SmtpServer.Send(mail);
}
Here's the error:
The SMTP server requires a secure connection or the client was not authenticated. The server response was: SMTP authentication is required.
Looking at other questions I tried what they suggested, to make SmtpServer.EnableSsl = true. This didn't work at all. It gave the following:
System.Net.Mail.SmtpException: Server does not support secure connections.
I'm guessing I should disable SSL and have it the way it was before.
Any suggestions how to make email sending work again?
EDIT
I've tried without SmtpServer.UseDefaultCredentials = false;
I've tried with it set to true: SmtpServer.UseDefaultCredentials =true;
I've tried commenting that line along with the following //SmtpServer.Credentials = new System.Net.NetworkCredential(emailUsername, emailPassword);

That error message is typically caused by one of the following:
Incorrect connection settings, such as the wrong port specified for the secured or non-secured connection
Incorrect credentials. I would verify the username and password combination, to make sure the credentials are correct.

If you are sure that your Username and Password are correct, but you still get errors then it means that Gmail has blocked your application. Allow less secure apps in your Google Account settings
Visit this link to your Google Account settings for Less Secure App access.
Select your Google Account from which you are sending the mail.
Set Allow less secure apps to ON.

I think you have to set DeliveryMethod = SmtpDeliveryMethod.Network
this one is currently working in my PC, just i checked,working nice,try this
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);
}

You need to create an app password so that your application can bypass 2FA:
Sign in with App Passwords
Google App Password

If you are deploying the application on a server, try logging in your google account in your server. Bizarre thing is, smtp email sending app works fine in my desktop. Not in the server. This might be affected by how google's security mechanism works.

How to send mails using SmtpClient and DefaultNetworkCredentials to a distribution list that only allows authenticated senders?

I'm trying to send automated emails from a C# console application from machines to clients all on the same domain via our internal Exchange 2007 server (using SMTP), but I'm hitting a snag with distribution lists that only allow authenticated senders. Basically the mails I'm sending are getting rejected by Exchange with:
#550 5.7.1 RESOLVER.RST.AuthRequired; authentication required ##rfc822;AuthTESTGroup#example.com
I'm using System.Net.Mail.SmtpClient and setting the Credentials property to System.Net.CredentialCache.DefaultNetworkCredentials, but somewhere along the line, the credentials of the account running this program (me, a valid domain user with a valid mailbox) are not getting passed down to Exchange correctly.
I'm using System.Net.CredentialCache.DefaultNetworkCredentials because I do not want to hard code a username or password (either in the code itself or in any sort of configuration file); I want the process to authenticate with our SMTP server using Windows authentication.
Here is a test program I've been using to reproduce the problem (domain names have been anonomized):
using System;
using System.Net.Mail;
namespace ConsoleApplication1
{
class Program
{
static void Main()
{
var smtpClient = new SmtpClient
{
Host = "MAIL",
Port = 25,
DeliveryMethod = SmtpDeliveryMethod.Network,
Credentials = System.Net.CredentialCache.DefaultNetworkCredentials
};
var mailMessage = new MailMessage
{
Body = "Testing",
From = new MailAddress(Environment.UserName + "#example.com"),
Subject = "Testing",
Priority = MailPriority.Normal
};
mailMessage.To.Add("AuthTESTGroup#example.com");
smtpClient.Send(mailMessage);
}
}
}
Whenever I run this as myself (again, I'm a valid user on the domain, with an existing mailbox on the Exchange server) I get an undeliverable bounce message from Exchange with the response:
#550 5.7.1 RESOLVER.RST.AuthRequired; authentication required ##rfc822;AuthTESTGroup#example.com
I talked to our Exchange server admin and he saw the following error from the Exchange server's event log:
Account For Which Logon Failed:
Security ID: NULL SID
Account Name:
Account Domain:
Failure Information:
Failure Reason: Unknown user name or bad password.
Status: 0xc000006d
Sub Status: 0xC0000064
Apparently that status code and sub status code translate to:
0xc000006d This is either due to a bad username or authentication information. Usually logged as status code with 0xc0000064 as substatus
0xC0000064 user name does not exist
So again, it's as if somewhere along the line, my Windows credentials are not getting passed down to the Exchange server even though I'm setting the SmtpClient.Credentials to System.Net.CredentialCache.DefaultNetworkCredentials
Any ideas?
Thanks in advance!

you need to pass username, password
here is a code snippet of how I would do it... keep in mind this is a code snippet you need to make the necessary changes to fit your Use Case
MailClient = new SmtpClient();
MailClient.Credentials = new System.Net.NetworkCredential(username, password);
below is another example but uses the server variable.. this maybe what you need to do try and let me know the server for example you can pass as your domain.com
example :
//SmtpClient client = new SmtpClient("smtp.contoso.com");//this would be server
//client.Credentials = CredentialCache.DefaultNetworkCredentials;
public static void CreateBccTestMessage(string server)
{
MailAddress from = new MailAddress("ben#contoso.com", "Ben Miller");
MailAddress to = new MailAddress("jane#contoso.com", "Jane Clayton");
MailMessage message = new MailMessage(from, to);
message.Subject = "Using the SmtpClient class.";
message.Body = #"Using this feature, you can send an e-mail message from an application very easily.";
MailAddress bcc = new MailAddress("manager1#contoso.com");
message.Bcc.Add(bcc);
SmtpClient client = new SmtpClient(server);
client.Credentials = CredentialCache.DefaultNetworkCredentials;
Console.WriteLine("Sending an e-mail message to {0} and {1}.",
to.DisplayName, message.Bcc.ToString());
try
{
client.Send(message);
}
catch (Exception ex)
{
Console.WriteLine("Exception caught in CreateBccTestMessage(): {0}",
ex.ToString());
}
}