What is the best way to track defect sources in tfs?

We have various teams for a project like the vulnerability team, the customer, pre-sales, etc. We give a build and these teams independently test it. They do not have access to our tfs system. So they usually send in their defects via email. It will usually be send in an excel format. Our testing team takes these up and logs them into tfs.

Sometimes they modify the original defect description (in excel) and add the expected/actual results. Sometimes they miss to cite the source. I am talking about managing the various sources as such.

Is there a way we can add these sources into tfs, and actually link this particular source with the defects, with individual comments associated with them (saying where in the source we can find the actual material for the defect).

Edit:

I don't know if there is a way to manage various sources. Consider this: the vulnerability assessment team has come out with defects/suggestions. They captured it into an excel and passed that on to the testing team (in my case). The testing team takes the responsibility of elaborating the defect and logging it in tfs. Now say that the excel has come with 20 defect items. This is my source. (It answers the question where did this defect come from). So ultimately when I am looking at a bug I know from where it came from - I'll ultimately be looking at the email sent from the VA team which has the excel or the excel file itself sent by the VA team.

It may be one of the 20 items in that excel. How should the tester link to this source just once? On the contrary, it does not make sense for the tester to attach the same excel 20 times (i.e. attach the same excel for the 20 defects while logging it into tfs) right? I hope you get my point.