defaultAdAlertDest= ['hsingh@gmail.com" "hariom.singh@gmail.com']

["hsingh@arinc.com","hariom.singh@rockwellcollins.com"]

val = ','.join(str(x) for x in defaultAdAlertDest)
  new_list = val.split(" ")

In [31]: new_list
Out[31]: ['hsingh@gmail.com"', '"hariom.singh@gmail.com']

with all the garbled quotation marks