Add support for custom SMTP greeting message

[tinohager]

Introduces a CustomGreetingMessage property to ISmtpServerOptions and SmtpServerOptionsBuilder, allowing configuration of the initial SMTP greeting sent to clients. SmtpSession now uses this custom message if set, otherwise defaults to the standard greeting with server name and version.

Fix issue

• Add option to hide SmtpServer version #187

An example of the server configuration

var options = new SmtpServerOptionsBuilder()
    .ServerName("SMTP Server")
    .Port(9025)
    .CustomGreetingMessage("Hi")
    .Build();

220 SMTP Server Hi

[cosullivan]

maybe this should actually be something like

Func<ISmtpContext, string> CustomGreetingMessage

which would give the ability to make the message dynamic?

[tinohager]

I've already thought about it. I think the only variable that is interesting is the version number but this is not in the SmtpContext.

[cosullivan]

I've already thought about it. I think the only variable that is interesting is the version number but this is not in the SmtpContext.

I think its worth changing this to a function as people might want to rotate greeing messages or customize it somehow... even if what they need isnt in the context, they will still have customization if this is a function.

[tinohager]

An example of the server configuration

var options = new SmtpServerOptionsBuilder()
    .ServerName("SMTP Server")
    .Port(9025)
    .CustomGreetingMessage(MyCustomGreeting)
    .Build();

private static string MyCustomGreeting(ISessionContext context)
{
    return $"220 {context.ServerOptions.ServerName} hello";
}

220 SMTP Server Hi

[tinohager]

@cosullivan Is this what you had in mind?

It would now also be possible to return the following in the greeting during maintenance

554 Service unavailable