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hpn-270-tdp@e-net.nara.jp: host aspmx.l.google.com[2607:f8b0:4023:1411::1b] said: 550-5.7.1 The user or domain that you are sending to (or from) has a policy that 550-5.7.1 prohibited the mail that you sent. Please contact your domain 550-5.7.1 administrator for further details. For more information, go to 550 5.7.1 https://support.google.com/a/answer/172179 o2-20020a056902110200b00dc2473acf93si4560717ybu.600 - gsmtp (in reply to end of DATA command)