Here is the method I've found works the best for me. I used to just link to the subfolder but found some international users experienced huge lag and even crashed there inbox. I switched to the below so that the image was imbedded in the email and it solved the lag issues because the file is actually embedded in the email.
Sub sendKeyMailer()
Dim emlMsg As Object
Set emlMsg = CreateObject("CDO.Message")
strBody = "<html> yadda yadda tricks are for kids. <br><br>"
strBody = strBody & "<img src=""cid:myimage.jpg""><BR><BR>"
strBody = strBody & "but tricks make the world go round.</html>"
emlMsg.Configuration.Fields.Item("http://schemas.microsoft.com/cdo/configuration/sendusing") = 2
emlMsg.Configuration.Fields.Item("http://schemas.microsoft.com/cdo/configuration/smtpserver") = "<<yourserver>>"
emlMsg.Configuration.Fields.Item("http://schemas.microsoft.com/cdo/configuration/smtpserverport") = 25
emlMsg.Configuration.Fields.Update
emlMsg.AddRelatedBodyPart "C:\temp\The Big Eskimo Roll.jpg", "myimage.jpg", cdoRefTypeId
emlMsg.Fields.Item("urn:schemas:mailheader:Content-ID") = "<myimage.jpg>"
emlMsg.Fields.Update
With emlMsg
.To = "allthepeople@yourcompany.com"
.From = "aGrpLst@yourcompany.com"
.Subject = "Humpty dumpty had a great fall" '''I have kids....;^D.....
.HTMLbody = strBody
'.AddAttachment "C:\temp\The Big Eskimo Roll.jpg"
.Send
End With
Set emlMsg = Nothing
End Sub