Hi,

This is my main mail server: 103.11.22.200 
And this is outgoing gateway mail server: 115.37.121.88

In 103.11.22.200's smartermail gateway config:
Option:
Server's address: 115.37.121.88
Port: 80
Encryption: SSL

Type: round robin
Enabled authentication:
Username: Administrator
Password: xxxxxxx
Smartermail gateway:
Enabled smartermail gateway mode
Smartermail URL: https://115.37.121.88 
Smartermail Username: Administrator 

Smartermail Password: xxxxxxx 

Then I create an email in 103.11.22.200 to send out, delivery.log show me this:

11:29:52.102 [94002] Connection to 115.37.121.88:80 from 103.11.22.200:50709 succeeded (Id: 1)
11:29:52.102 [94002] Exception: The handshake failed due to an unexpected packet format.
   at System.Net.Security.SslState.StartReadFrame(Byte[] buffer, Int32 readBytes, AsyncProtocolRequest asyncRequest)
   at System.Net.Security.SslState.StartReceiveBlob(Byte[] buffer, AsyncProtocolRequest asyncRequest)
   at System.Net.Security.SslState.CheckCompletionBeforeNextReceive(ProtocolToken message, AsyncProtocolRequest asyncRequest)
   at System.Net.Security.SslState.ForceAuthentication(Boolean receiveFirst, Byte[] buffer, AsyncProtocolRequest asyncRequest)
   at System.Net.Security.SslState.ProcessAuthentication(LazyAsyncResult lazyResult)
   at MailService.RelayServer.Clients.SMTP.ClientConnectionSync.InitiateSsl(Boolean validateAllCerts)
   at MailService.RelayServer.Clients.SMTP.SmtpClientSession.Initialize(String senderAddress, List`1 recipientList, String destServerIP)
11:29:52.102 [94002] Failed to send to IP 115.37.121.88 , error string: Attempted to send the message to the following IPs:
    115.37.121.88 
11:29:52.117 [94002] Removed from RemoteDeliveryQueue (0 queued or processing)

Can you help me on this error?