There's really not much to add to Fredrik's answer, but I'm afraid you might be looking at the wrong pieces of his solution. I just tested it myself, and it's working just fine, so here's the result, step-by-step:
my xpage is bound to a Notes form named testMail using a document datasource called mailDoc. It is built like this:
Control#1 is a textarea with a multiple separator set to a comma, so that I can enter multiple mail addresses separated by commas. The textarea is bound to a Notes field named SendTo:
<xp:inputTextarea
value="#{mailDoc.SendTo}"
id="sendTo1"
multipleSeparator=",">
</xp:inputTextarea>
Control #2 is a simple EditBox control bound to a Notes field named Subject:
<xp:inputText
value="#{mailDoc.Subject}"
id="subject1">
</xp:inputText>
A button control labelled Save & Send first saves the current document if it is New (i.e. has never been saved before), then performs all the necessary steps to send a doclink for the currently opened doc (button's onclick event); in the following code I'm using these variables:
mailDoc = my datasource object;
thisdoc = the backend doc object that the datasource is bound to;
tempdoc = a temp backend doc object used to be sent via Notes mail:
if(mailDoc.isNewNote()){
mailDoc.save();
}
var thisdoc = mailDoc.getDocument();
var tempdoc = database.createDocument();
tempdoc.replaceItemValue("Form", "Memo");
tempdoc.replaceItemValue("SendTo", thisdoc.getItemValue("SendTo"));
tempdoc.replaceItemValue("Subject", thisdoc.getItemValue("Subject"));
var tempbody:NotesRichtextItem = tempdoc.createRichTextItem("Body");
tempbody.appendText("This is my Mail, click on the doc link below to open the original doc:")
tempbody.addNewLine(2);
tempbody.appendDocLink(thisdoc);
tempdoc.send();
thisdoc.recycle();
tempbody.recycle();
tempdoc.recycle();
Result: the button code sends a mail containing a Notes document link to all the recipients that I previously entered in the SendTo field.
If I set the testMail form's property to use the Xpage in Notes (Defaults >> On Open >> Display Xpage instead >> mailSendTest), then this also works for the XPinc version. And if the recipient then clicks on the doc link the originating document of course opens in XPinc mode as well.
Remark:
I need to save the originating doc at least once otherwise the appended doc link might not be usable for the recipients; could this have been the reason why Fredrik's answer didn't work for you?
Hope this helps. If this is working for you please accept Fredrik's answer.
Update:
Changed some variable names in my code example to clarify things