Exchange 2010 user Non-deliverable message

Question

Any help is appreciated. We have a user who is trying to email a vendor who she normally can but now she is getting an NDR message stating:
The following organization rejected your message: [XXX]. <- other company's IP
Diagnostic information for administrators:
Generating server:
esa1.XXX.iphmx.com  <- our server
Recipient's email address
[XXX] <- other company's IP #<[XXX] <- other company's IP #5.0.0 smtp;
5.3.0 - Other mail system problem 550-'permanent failure for one or more
recipients (recipients email address:blocked)' (delivery attempts: 0)>
#SMTP#
Original message headers:
X-IronPort-AV:
E=Sophos;i="4.84,830,1355126400";
d="xml'?bin'?scan'208,217,72,48?xlsx'208,217,72,48,72,48?rels'208,217,72,48,72,48";a="8561738"
Received:
from firewall01.XXX.com (HELO  <- our company's system
webmail.XXX.com) <- our company's system
([IP]) by esa1.XXX.iphmx.com <- our company's system 
with ESMTP; 12 Mar 2013
04:30:48 -0800
Received: from
TMIEXMB02.XXX.com ([IP])  <- our company's system
by
TMIEXCAS02.XXX.com ([IP]) with mapi id  <- our company's system
14.02.0247.003;

Answer 1

Any help is appreciated. We have a user who is trying to email a vendor who she normally can but now she is getting an NDR message stating:
The following organization rejected your message: [XXX]. <- other company's IP
Diagnostic information for administrators:
Generating server:
esa1.XXX.iphmx.com  <- our server
Recipient's email address
[XXX] <- other company's IP #<[XXX] <- other company's IP #5.0.0 smtp;
5.3.0 - Other mail system problem 550-'permanent failure for one or more
recipients (recipients email address:blocked)' (delivery attempts: 0)>
#SMTP#
This NDR is stating that the recipient company has blocked this email address so you will have to contact them to see if they can lift the block or why it was blocked in the first place.
Jason Apt, Microsoft Certified Master | Exchange 2010
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