Adding a "Message-Id" header to an email created using C#

Question

_{Saturday, July 14, 2018 8:15 AM}

Google recommend that emails sent to @gmail.com addresses include a valid Message-Id in the header - otherwise Google may treat the email as spam.  And observation suggests the latter is indeed true.

How do I add a Message-Id line to the email header, when creating the email using C# (or outlook.application)?

All replies (5)

_{Saturday, July 14, 2018 1:42 PM ✅Answered}

If you are using System.Net.Mail to send your messages, then you can access the collection of headers by means of the property Headers of the MailMessage object.

/en-us/dotnet/api/system.net.mail.mailmessage.headers?view=netframework-4.7.1#System_Net_Mail_MailMessage_Headers

Simply do .Add on the collection to add any headers that you want.

_{Saturday, July 14, 2018 7:57 PM}

Thank you for that.  I had kind of assumed that the Headers property was read-only, but you have now pointed out that that is not so.  I'll follow this up further.

_{Saturday, July 14, 2018 9:17 PM}

Yes, the Headers property itself is read-only... but it returns a NameValueCollection, and this one is not read-only -- you can add entries to the collection.

_{Sunday, July 15, 2018 12:24 AM}

Here is another resource http://www.systemnetmail.com/faq/3.3.4.aspx

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VB Forums - moderator

_{Sunday, July 22, 2018 4:09 PM}

Alberto

Yes that did work - in a C# console test program.  However, my application is written in Visual FoxPro and currently uses Outlook via COM to send the email. So I tried to create a C# DLL that could be called from VFP, in place of using Outlook COM, but failed to get the two to work together.

Nevertheless, I also send emails from a C# Windows service, and your input will be useful there.