We have used the SendMail routine in DotNetNuke for years. After upgrading to DNN 5.4.4, we noticed that the emails coming from some of our modules were stipping out the HTML links.
For example: DotNetNuke.Services.Mail.Mail.SendMail("support@domain.com", "support@domain.com", String.Empty, "URL Test", "this is a test of dnnmail: <a href='http://www.dotnetnuke.com'>DotNetNuke</a>", String.Empty, "html", String.Empty, String.Empty, String.Empty, String.Empty) This will result in an email like: "this is a test of dnnmail: DotNetNuke " Previously the result would be: "this is a test of dnnmail: DotNetNuke"
After spending countless hours trying to find in our code where this issue was happening, I realized that on a site that had not been upgraded it was working correctly. After adding some code to test this, I have confirmed that indeed the latest version of DotNetNuke is stripping out links from HTML emails.
I have added a task to Gemini:
http://support.dotnetnuke.com/issue/ViewIssue.aspx?id=12926&PROJID=2
I hope this makes it into the DNN 5.5.0 release, otherwise we will be writing our own SendMail routine... which we don't want to do.