{"id":1009,"date":"2013-08-13T12:00:37","date_gmt":"2013-08-13T10:00:37","guid":{"rendered":"http:\/\/www.limilabs.com\/blog\/?p=1009"},"modified":"2014-04-09T15:28:01","modified_gmt":"2014-04-09T13:28:01","slug":"the-handshake-failed-due-to-an-unexpected-packet-format","status":"publish","type":"post","link":"https:\/\/www.limilabs.com\/blog\/the-handshake-failed-due-to-an-unexpected-packet-format","title":{"rendered":"The handshake failed due to an unexpected packet format"},"content":{"rendered":"

Most likely your server requires explicit SSL<\/strong>, sometimes also known as TLS. <\/p>\n

It is called explicit SSL mode, because after the connection is established, client explicitly issues a command to the server that initiates SSL\/TLS negotiation.<\/p>\n

This is in contrast to implicit SSL mode, where SSL negotiation is initiated just after successful connection. In implicit mode server and client knows to use SSL, because client uses default protocol port<\/a>, that is commonly used for secured traffic.<\/p>\n

First try to connect to your server without SSL:<\/p>\n

\r\n\/\/ C#\r\n\r\nclient.Connect("mail.example.com");\r\n<\/pre>\n
\r\n' VB.NET\r\n\r\nclient.Connect("mail.example.com")\r\n<\/pre>\n
Then, before logging-in, start explicit SSL negotiation<\/strong>. The command name differs for different protocols:<\/p>\n
Explicit SSL (aka TLS)<\/h2>\n
The code is exactly the same no matter which protocol (IMAP, POP3 or SMTP) you use.<\/p>\n
\r\n\/\/ C#\r\n\r\nclient.Connect("mail.example.com");\r\nclient.StartTLS();\r\n<\/pre>\n
\r\n' VB.NET\r\n\r\nclient.Connect("mail.example.com")\r\nclient.StartTLS()\r\n<\/pre>\n
StartTLS<\/em> method negotiates security protocol with the server and secures the channel using SSL or TLS. Now, your connection is secured<\/strong>. <\/p>\n
\nHere you can find more details on SSL vs TLS vs STARTTLS<\/a>.\n<\/div>\n
Please note, that your server may not need SSL\/TLS at all. In such case simply use Connect<\/em> method.<\/p>\n
Enabled SSL Protocols<\/h2>\n
On very rare occasions “handshake failed…” error may indicate that TLS is incorrectly configured on the client machine or on the server. <\/p>\n
It is possible to force SSL v3.0 usage instead of TLS in explicit mode:<\/p>\n
\r\n\/\/ C#\r\n\r\nclient.SSLConfiguration.EnabledSslProtocols = SslProtocols.Ssl3;\r\nclient.Connect("mail.example.com");\r\nclient.StartTLS();\r\n<\/pre>\n
\r\n' VB.NET\r\n\r\nclient.SSLConfiguration.EnabledSslProtocols = SslProtocols.Ssl3;\r\nclient.Connect("mail.example.com");\r\nclient.StartTLS();\r\n<\/pre>\n
It is also possible to force SSL v3.0 usage instead of TLS in implicit mode:<\/p>\n
\r\n\/\/ C#\r\n\r\nclient.SSLConfiguration.EnabledSslProtocols = SslProtocols.Ssl3;\r\nclient.ConnectSSL("mail.example.com");\r\n<\/pre>\n
\r\n' VB.NET\r\n\r\nclient.SSLConfiguration.EnabledSslProtocols = SslProtocols.Ssl3;\r\nclient.ConnectSSL("mail.example.com");\r\n<\/pre>\n
Self-signed certificates<\/h2>\n
Remember that you can ignore SSL certificate errors<\/strong> using ServerCertificateValidate <\/em>event:<\/p>\n
\r\n\/\/ C#\r\n\r\nstatic void Validate(\r\n    object sender,\r\n    ServerCertificateValidateEventArgs e)\r\n{\r\n    const SslPolicyErrors ignoredErrors =\r\n        SslPolicyErrors.RemoteCertificateChainErrors |\r\n        SslPolicyErrors.RemoteCertificateNameMismatch;\r\n\r\n    if ((e.SslPolicyErrors & ~ignoredErrors) == SslPolicyErrors.None)\r\n    {\r\n        e.IsValid = true;\r\n        return;\r\n    }\r\n    e.IsValid = false;\r\n}\r\n\r\nclient.ServerCertificateValidate += Validate;\r\nclient.Connect...\r\n<\/pre>\n
\r\n' VB.NET\r\n\r\nPrivate Sub ValidateCerificate( _\r\n    ByVal sender As Object, _\r\n    ByVal e As ServerCertificateValidateEventArgs)\r\n\r\n    Const ignoredErrors As SslPolicyErrors = _\r\n        SslPolicyErrors.RemoteCertificateChainErrors Or _\r\n        SslPolicyErrors.RemoteCertificateNameMismatch\r\n\r\n    If (e.SslPolicyErrors And Not ignoredErrors) = SslPolicyErrors.None Then\r\n        e.IsValid = True\r\n        Return\r\n    End If\r\n    e.IsValid = False\r\nEnd Sub\r\n\r\nAddHandler client.ServerCertificateValidate, AddressOf Validate\r\nclient.Connect...\r\n<\/pre>\n","protected":false},"excerpt":{"rendered":"
Most likely your server requires explicit SSL, sometimes also known as TLS. It is called explicit SSL mode, because after the connection is established, client explicitly issues a command to the server that initiates SSL\/TLS negotiation. This is in contrast to implicit SSL mode, where SSL negotiation is initiated just after successful connection. In implicit […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4],"tags":[15,28,42,50,53,83,57],"class_list":["post-1009","post","type-post","status-publish","format-standard","hentry","category-mail-dll","tag-c","tag-imap","tag-pop3","tag-smtp","tag-ssl","tag-tls","tag-vb-net"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/www.limilabs.com\/blog\/wp-json\/wp\/v2\/posts\/1009"}],"collection":[{"href":"https:\/\/www.limilabs.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.limilabs.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.limilabs.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.limilabs.com\/blog\/wp-json\/wp\/v2\/comments?post=1009"}],"version-history":[{"count":11,"href":"https:\/\/www.limilabs.com\/blog\/wp-json\/wp\/v2\/posts\/1009\/revisions"}],"predecessor-version":[{"id":3965,"href":"https:\/\/www.limilabs.com\/blog\/wp-json\/wp\/v2\/posts\/1009\/revisions\/3965"}],"wp:attachment":[{"href":"https:\/\/www.limilabs.com\/blog\/wp-json\/wp\/v2\/media?parent=1009"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.limilabs.com\/blog\/wp-json\/wp\/v2\/categories?post=1009"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.limilabs.com\/blog\/wp-json\/wp\/v2\/tags?post=1009"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}