I am using sendmail to send mail but for gmail i am getting service unavailable
maillog
Aug 14 09:52:24 ip-172-31-25-85 sendmail[1361]: STARTTLS=client, relay=gmail-smtp-in.l.google.com., version=TLSv1/SSLv3, verify=FAIL, cipher=ECDHE-RSA-AES128-GCM-SHA256, bits=128/128
Aug 14 09:52:25 ip-172-31-25-85 sendmail[1361]: w7E9qLvM001359: to= <test@gmail.com>, ctladdr=<apache@ip-172-31-25-85.ap-southeast- 1.compute.internal> (48/48), delay=00:00:04, xdelay=00:00:01, mailer=esmtp, pri=187579, relay=gmail-smtp-in.l.google.com. [172.217.194.27], dsn=5.0.0, stat=Service unavailable
Some days back i tested it was working for gmail but suddenly it stopped working