As in this?
Then yes hard/soft edges in Maya can be though of as being a form of smoothing but is not a smoothing group in the way 3ds Max does it and as expected by Unreal 4.
It should also be noted that smoothing groups can become rather fragile where it becomes next to impossible for the object to even accept and maintain the grouping as expected.
A some what know cause is extensive editing of an object can can do nasty things to geometry surfacing in 3ds Max that you can not see in the view port so at some point you might have to rebuild the object from scratch.
As I mentioned though you could test by flipping switch’s in the export/import process but it’s been my experience that once the SG’s are bonked you might as well rebuild.
P.S. It should also be noted that re-importing a object that you think has been fixed does not import the edits and it “seems” to me that a re-import does not always included changes to the SG’s so best practice always delete the current object and import a clean from scratch version.