[CentOS] Sendmail log entries

Recently we began seeing lots of these log entries on our off-site mx
smtp host.  I have googled this but I am not clear from what I have
read if this is something we can stop altogether or should even worry
about.

Comments?

Logwatch.  .  .

 --------------------- sendmail Begin ------------------------

 SMTP SESSION, MESSAGE, OR RECIPIENT ERRORS
 ------------------------------------------

 WARNING!!!!  Possible Attack:
    Attempt from 104.Red-83-50-106.dynamicIP.rima-tde.net
[83.50.106.104] with:
       command=HELO/EHLO, count=3: 1 Time(s)


-- 
***          E-Mail is NOT a SECURE channel          ***
James B. Byrne                mailto:ByrneJB at Harte-Lyne.ca
Harte & Lyne Limited          http://www.harte-lyne.ca
9 Brockley Drive              vox: +1 905 561 1241
Hamilton, Ontario             fax: +1 905 561 0757
Canada  L8E 3C3