Not receiving email from Zoom

Our own hosted Sendmail server gives the following problem :- 

Dec 23 13:50:34 mx01 sendmail[10474]: 1BN8KXZN010474: o4.sg.zoom.us [149.72.198.96] did not issue MAIL/EXPN/VRFY/ETRN during connection to MTA
Dec 23 14:07:59 mx01 sendmail[11058]: 1BN8bx3k011058: o6.sg.zoom.us [149.72.249.102] did not issue MAIL/EXPN/VRFY/ETRN during connection to MTA

Problem persists only with Zoom Server.  Emails from others are coming through.