Forwaring rule to server with STARTTLS not supported

[osjoberg]

Thank you for Papercut! We use Papercut during development, and use forwarding rules to debug complicated email layouts on smartphones.

However, our SMTP server (Exchange) does not support SSL, it supports STARTTLS.

If I change RelayRuleExtensions:35 from

client.Connect(forwardRule.SmtpServer, forwardRule.SmtpPort, forwardRule.SmtpUseSSL);

to

client.Connect(forwardRule.SmtpServer, forwardRule.SmtpPort, forwardRule.SmtpUseSSL ? SecureSocketOptions.Auto : SecureSocketOptions.None);

it works with our SMTP server. However I am not too familiar with the SMTP protocol or MailKit. It is possible that SecureSocketOptions.Auto may fail the negotiation where SecureSocketOptions.SslOnConnect would have worked.

Maybe there should be an option to explicitly select STARTTLS for the rules?

[osjoberg]

Follow up thought: System.Net.Mail.SmtpClient.EnableSsl does not seem to make a distinction between STARTTLS or SSL. When you set EnableSsl to true you actually tell the client to negotiate the encryption with the SMTP server. The developer does not need to know what type of encryption that is used. If MailKit SmtpClient can negotiate as well as System.Net.Mail.SmtpClient, the fix suggested above should be enough to solve this issue without complicating the user interface.