Issue with attach to email button after upgrade to windows 10

hello all,

facing a strange issue here after upgrading OS from windows 7 64 bit to windows 10 64 bit.

acrobat DC will not attach to email unless my outlook is closed. this is replicated also with other pdf software, and on other computers that have recently been upgraded from win 7 to win 10.

already tried to delete all other values except outlook in hkey local machine\software\clients\mail - this did not work.

also reset outlook settings in regedit - did not work either.

system details:

windows 10 64 bit (upgraded from windows 7 64 bit)

acrobat reader DC

office 2010 - outlook 2010 (same issue also happens with outlook 2013 on another computer)