Send mail error

[Dhaval Thakkar]

Any one has any idea about this error, I am not able to send email, getting below in send mail log

Mar 13 16:42:33 ady sendmail[13026]: x2DKgXU4013024: to=<dhava...@gmail.com>, ctladdr=<root@ady> (0/0), delay=00:00:00, xdelay=00:00:00, mailer=esmtp, pri=120330, relay=gmail-smtp-in.l.google.com. [IPv6:2a00:1450:4013:c01::1b], dsn=5.0.0, stat=Service unavailable

Mar 13 16:42:33 ady sendmail[13026]: x2DKgXU4013024: x2DKgXU4013026: DSN: Service unavailable

Mar 13 16:42:33 ady sendmail[13026]: x2DKgXU4013026: to=<root@ady>, delay=00:00:00, xdelay=00:00:00, mailer=local, pri=31549, dsn=2.0.0, stat=Sent