{"id":1299,"date":"2010-10-25T15:46:49","date_gmt":"2010-10-25T13:46:49","guid":{"rendered":"http:\/\/www.limilabs.com\/blog\/?p=1299"},"modified":"2014-06-23T17:40:53","modified_gmt":"2014-06-23T15:40:53","slug":"send-signed-email-using-smime","status":"publish","type":"post","link":"https:\/\/www.limilabs.com\/blog\/send-signed-email-using-smime","title":{"rendered":"Send signed email using S\/MIME"},"content":{"rendered":"

In this article we’ll show how to digitally sign email message and send it using Mail.dll email component<\/a>. You’ll need to use S\/MIME (sometimes called SMIME) standard to sign email.<\/p>\n

S\/MIME (Secure\/Multipurpose Internet Mail Extensions) is a standard for public key encryption and signing of any MIME data including email messages.<\/p>\n

S\/MIME was originally developed by RSA Data Security. Specification uses Cryptographic Message Syntax (CMS), an IETF specification that is identical in most respects with PKCS #7. <\/p>\n

S\/MIME provides the following cryptographic security services for electronic messaging applications: authentication, message integrity, non-repudiation of origin (using digital signatures<\/strong>), privacy and data security (using encryption). <\/p>\n

S\/MIME signatures are usually done with what’s called “detached signatures”. The signature information is separate from the text being signed. The MIME type for such signed data is multipart\/signed with the second part having a MIME subtype of application\/(x-)pkcs7-signature. Mail.dll uses application\/x-pkcs7-signature MIME entity to store S\/MIME detached signatures.<\/p>\n

Signing using MailBuilder<\/h2>\n
\r\n\/\/ C# version\r\n\r\nMailBuilder b = new MailBuilder();\r\nb.From.Add(new MailBox("mail@in_the_certificate.com", "Alice"));\r\nb.To.Add(new MailBox("bob@mail.com", "Bob"));\r\nb.Subject = "Test";\r\nb.Html =                            \/\/ Set HTML body\r\n    "This is <strong>signed<\/strong> message, " +\r\n    "with embedded image:<br \/>" +\r\n    "<img src = 'cid:image1' \/>.";\r\n\r\n\/\/ Read attachment from disk...and add it to Visuals collection\r\nMimeData image = b.AddVisual(@"c:\\image.jpg");\r\nimage.ContentId = "image1";\r\n\r\nb.SignWith(new X509Certificate2("TestCertificate.pfx", ""));\r\n\r\nIMail email = b.Create();\r\n<\/pre>\n
\r\n' VB.NET\r\n\r\nDim b As New MailBuilder()\r\nb.From.Add(New MailBox("mail@in_the_certificate.com", "Alice"))\r\nb.[To].Add(New MailBox("bob@mail.com", "Bob"))\r\nb.Subject = "Test"\r\n\r\n' Set HTML body\r\nb.Html = "This is <strong>signed<\/strong> message, " _\r\n   + "with embedded image:<br \/>" _\r\n   + "<img src = 'cid:image1' \/>."\r\n\r\n' Read attachment from disk...and add it to Visuals collection\r\nDim image As MimeData = b.AddVisual("c:\\image.jpg")\r\nimage.ContentId = "image1"\r\n\r\nb.SignWith(New X509Certificate2("TestCertificate.pfx", ""))\r\n\r\nDim email As IMail = b.Create()\r\n<\/pre>\n
Signing using fluent interface<\/h2>\n
\r\n\/\/ C# version\r\n\r\nIMail email = Mail\r\n    .Html(@"<html><body>This is <strong>signed<\/strong> message with image <img src = 'cid:image1' \/><\/body><\/html>")\r\n    .Subject("Test")\r\n    .From(new MailBox("mail@in_the_certificate.com", "Alice"))\r\n    .To(new MailBox("bob@mail.com", "Bob"))\r\n    .AddVisual(@"c:\\image.jpg")\r\n    .SetContentId("image1")\r\n    .SignWith(new X509Certificate2("TestCertificate.pfx", ""))\r\n    .Create();\r\n<\/pre>\n
\r\n' VB.NET\r\n\r\nDim email As IMail = Mail _\r\n    .Html("<html><body>This is <strong>signed<\/strong> message with image <img src = 'cid:image1' \/><\/body><\/html>") _\r\n    .Subject("Test") _\r\n    .From(New MailBox("mail@in_the_certificate.com", "Alice")) _\r\n    .[To](New MailBox("bob@mail.com", "Bob")) _\r\n    .AddVisual(@"c:\\image.jpg") _\r\n    .SetContentId("image1") _\r\n    .SignWith(New X509Certificate2("TestCertificate.pfx", "")) _\r\n    .Create()\r\n<\/pre>\n
Create test certificate<\/h2>\n
You can use following commands in VisualStudio Command Prompt to create test certificate:<\/p>\n
makecert.exe -pe -r -sv Test_Keys.pvk -n \"CN=John Doe,E=email@in-the-certificate.com\" -sky exchange Test.cer<\/code><\/p>\n
pvk2pfx.exe -pvk Test_Keys.pvk -spc Test.cer -pfx Test.pfx<\/code><\/p>\n
\nIf you use CER or PEM files you can find more information in this article: 
\nImporting private\/public keys or certificates in PEM, CER formats<\/a>.\n<\/div>\n
Sending signed email using SMTP<\/h2>\n
Now we can connect to SMTP server and send the email we recently created:<\/p>\n
\r\n\/\/ C#\r\n\r\nusing (Smtp client = new Smtp())\r\n{\r\n    client.Connect("smtp.example.com"); \/\/ or ConnectSSL\r\n    client.UseBestLogin("user", "password");\r\n    client.SendMessage(email);\r\n    client.Close();\r\n}\r\n<\/pre>\n
\r\n' VB.NET\r\n\r\nUsing client As New Smtp()\r\n\tclient.Connect("smtp.example.com") ' or ConnectSSL\r\n\tclient.UseBestLogin("user", "password")\r\n\tclient.SendMessage(email)\r\n\tclient.Close()\r\nEnd Using\r\n<\/pre>\n
By default Mail.dll uses SHA-1 alghoritm for signing. You can change this setting and choose different signature and encryption algorithm while sending S\/MIME encrypted email message<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"
In this article we’ll show how to digitally sign email message and send it using Mail.dll email component. You’ll need to use S\/MIME (sometimes called SMIME) standard to sign email. S\/MIME (Secure\/Multipurpose Internet Mail Extensions) is a standard for public key encryption and signing of any MIME data including email messages. S\/MIME was originally developed […]<\/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":[15,33,49,50,57],"class_list":["post-1299","post","type-post","status-publish","format-standard","hentry","category-mail-dll","tag-c","tag-email-component","tag-smime","tag-smtp","tag-vb-net"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/www.limilabs.com\/blog\/wp-json\/wp\/v2\/posts\/1299"}],"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=1299"}],"version-history":[{"count":14,"href":"https:\/\/www.limilabs.com\/blog\/wp-json\/wp\/v2\/posts\/1299\/revisions"}],"predecessor-version":[{"id":4696,"href":"https:\/\/www.limilabs.com\/blog\/wp-json\/wp\/v2\/posts\/1299\/revisions\/4696"}],"wp:attachment":[{"href":"https:\/\/www.limilabs.com\/blog\/wp-json\/wp\/v2\/media?parent=1299"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.limilabs.com\/blog\/wp-json\/wp\/v2\/categories?post=1299"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.limilabs.com\/blog\/wp-json\/wp\/v2\/tags?post=1299"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}