Why mail in not sending for abc@xyz.com but working for abc@pqr.be

HI ,

Can some one help me for the mail which is getting trigger from SAP sourcing(staging) is getting fail for one something like abc@xyz.com but after changing the mail to abc@pqr.be ,mail is getting sent.I have  even checked all the whitespace special charecter  also.

All scenerio are woking fine in SAP Sourcing production.

Please suggest me.

Thanks

Peeyush Ranjan