strange emails on sendmail queue

[supportadl]

Hi to all. I see about 2.000 emails similar to this attached on my sendmail queue. I'm running Centos 5 and sendmail 8.13.8. All emails have status "Deferred" because destination address don't exist. I don't know how this emails arrive to my server. Only authenticated user can send mail from sendmail. I already test it. How can I see if some of my users try to send this emails? I'm not able to see this on maillog. I hope this is not a configuration error on my sendmail config file.

I have in logs some line like these:
Jun 9 14:09:46 adlhost60 sendmail[13547]: STARTTLS=client, relay="symailserver.hsbc.co.uk"., version=TLSv1/SSLv3, verify=FAIL, cipher=AES256-SHA, bits=256/256

Jun 9 14:09:47 adlhost60 sendmail[13547]: o59BnO3Q013547: to=<"email address attached">, delay=00:00:01, xdelay=00:00:01, mailer=esmtp, pri=32819, relay="symailserver.hsbc.co.uk" [193.108.72.62], dsn=5.1.1, stat=User unknown

Jun 9 14:19:34 adlhost60 sendmail[13547]: STARTTLS=client, relay="symailserver.hsbc.co.uk"., version=TLSv1/SSLv3, verify=FAIL, cipher=AES256-SHA, bits=256/256

Jun 9 14:19:35 adlhost60 sendmail[13547]: o59BnO3T013547: to=<"email address attached">, delay=00:00:01, xdelay=00:00:01, mailer=esmtp, pri=32819, relay="symailserver.hsbc.co.uk". [193.108.72.62], dsn=5.1.1, stat=User unknown

Jun 9 14:30:29 adlhost60 sendmail[13547]: STARTTLS=client, relay="symailserver.hsbc.co.uk"., version=TLSv1/SSLv3, verify=FAIL, cipher=AES256-SHA, bits=256/256

Jun 9 14:30:29 adlhost60 sendmail[13547]: o59BnO3W013547: to=<"email address attached">, delay=00:00:00, xdelay=00:00:00, mailer=esmtp, pri=32819, relay="symailserver.hsbc.co.uk". [193.108.72.62], dsn=5.1.1, stat=User unknown

And now I see that i'm blacklisted on Topian. My server ip is 194.20.145.8.

Can you help me with this issue?
Thanks a lot.