# example from E-utilities Quick Start
http://eutils.ncbi.nlm.nih.gov/entrez/eutils/epost.fcgi?db=gene&id=7173

RESULT:
<ePostResult><QueryKey>1</QueryKey><WebEnv>NCID_1_40313954_165.112.9.37_9001_1444325384_419498518_0MetA0_S_MegaStore_F_1</WebEnv></ePostResult>


RESULT:
# X16522 is the accession number for the same entry
http://eutils.ncbi.nlm.nih.gov/entrez/eutils/epost.fcgi?db=gene&id=X16522

<ePostResult><QueryKey>1</QueryKey><WebEnv>NCID_1_40327324_165.112.9.28_9001_1444325491_1565967352_0MetA0_S_MegaStore_F_1</WebEnv><ERROR>IDs contain invalid characters which was treated as delimiters.</ERROR></ePostResult>