MAIL/EXPN/VRFY/ETRN during connection to MTA
 

hi,
I am a compelte newbie in linux...I need to resolve the following issue...there is a relay server relay@cactus.com in our organisation that relays mails for another server bus-fal@cactus.com.
the mails sent from bus-fal@cactus.com are not being relayed byt the relay server.
here is the error that i got in /var/log/maillog/ from relay server.

Nov 6 01:09:58 relay sendmail[23959]: nA669s8r023959: [10.50.50.34] did not issue MAIL/EXPN/VRFY/ETRN during connection to MTA

please help...what do i need to do for the mails to be recieved by relay server...thanks...