Question

It seems that when you use SmtpClient class and MailMessage to send emails, everything works fine. And it does send it. However, some servers, such as your business Exchange Server or Gmail.com or whatever services, sometimes reject these emails (because they could be phishing sites or spam sites?)

I’m using this and a lot of places reject the email I believe:

SmtpClient smtp = new SmtpClient
{
 Host = smtpClient,
 Timeout = 40000, // 40 seconds
 DeliveryMethod = SmtpDeliveryMethod.Network
};

How do you work around this? Do you have to use login credentials to some recognized / white-listed server so that it is authorized and trusted email?

I could use something like GMAIL authentication, but my server should be allowed to send emails, it shouldn’t have to rely on gmail.

Answer 1

Long ago there were many servers on the Internet that provided the service delivery of e-mail without asking too many questions about who was using the service.
Then came the SPAMMERS!.
A server that was sending mail freely around the world was no longer a benefactor of the internet, but a problem.
Nowadays it is increasingly difficult to find a server that sends mail on the Internet without asking for credentials.

Your e-mail server (smtp.yourbusiness.com or whatever you want) does not trust you.
When you ask it to send an email for you, it wants to know who you are.

SmtpClient smtp = new SmtpClient  
smtp.Host = "smtp.yourbusiness.com"; 
NetworkCredential credentials = new NetworkCredential("your_user_name_on_smtpserver", "your_password_on_smtpserver"); 
smtp.Credentials = credentials;