Question : Whenever i am sending mail it returns back and i got the error message like above

i am using Cyberoam as mail server. when i am sending mail to other domain. i got error like host mail.itcplant.com[203.196.139.145] said: 554 RFC2821 bounces are administratively denied (in reply to MAIL FROM command)
please suggest.

Answer : Whenever i am sending mail it returns back and i got the error message like above

Sorry, I was confused as to which mail server your were connecting to.

I now assume 203.196.139.146 is not your mail server but rather the recipient's; in that case, it seems they have some sort of antispam system running and it is detecting your emails as spam.

I checked to see if your domainname or IP is listed in any RBL list (http://www.robtex.com/rbl/) and it appears your IP is listed on one of these lists. Perhaps clearing your IP from this list should help.