Is it possible to notify a patent examiner of possible conflict in a pending patent he is working on? That he may not have identified? Is is proper for anyone to notify the examiner if they are concerned that the examiner may have missed a potenical conflict with registered patent already out there.
If by conflict you mean a prior art reference the examiner may not find you can do a third party submission under 35 U.S.C. 122(e). That was enacted with the AIA and provides a formal way to submit prior art to the attention of an examiner during a window of time.
Under 35 U.S.C. 122(e), such submissions may be made before (1) the later of (i) 6 months after the date of publication or (ii) the date of a first Office action on the merits rejecting any claims, or (2) before the date of a notice of allowance, if earlier. Section 122(e) also provides for such fees as the Director may prescribe. This new provision was effective on September 16, 2012, and applies to any patent application.
It was actually part of the origin story of Ask Patents SE. Then director of the USPTO, Dave Kappos, thought the collective knowledge of software practices by the SE user base could help unearth references the examiner might not find in the normal places they looked. This AIA provision was the first time there was a mechanism to put something in front of the examiner that the examiner is required to consider.
If the prior art you are thinking about is an issued US patent it is not likely to be missed by a US examiner.