email - Sending *.exe by changing extension failed

I know you can send .exe through email by changing their extension. I've been using this often. But strange thing happen when I tried to send this specific ".exe" file. It failed!!

It's this compressor, uharc.exe. Full app can be downloaded from here. I just need the uharc.exe that you can find in the bin folder.

Actually, failure didn't occure at gmail (I'm using it). But the recipient has rejected it (the recipient is in some private network). But how can the recipient identify that particular file only! Well, i haven't tried sending exe's before, but I've sent jar files which were rejected if I send without changing the extension..

Can anyone explain how's this happening. Is there any solution for this...(please note that the recipient's machine has strictly limited access. Can't download, install, even web surfing is much limited.. and that's why I'm doing this..)

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This is what gmail said about the failure..

Delivery to the following recipient failed permanently:

     ***@***.com

Technical details of permanent failure:
Google tried to deliver your message, but it was rejected by the recipient domain. We recommend contacting the other email provider for further information about the cause of this error. The error that the other server returned was: 550 550 5.7.1 Error: content rejected (state 17).

----- Original message -----

DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
        d=gmail.com; s=20120113;
        h=mime-version:date:message-id:subject:from:to:content-type;
        bh=QEk6/JzSwEYG+xPfJ5u4hmg00M3ANp+9zuGfwUNsWJ4=;
        b=DXcn1PO//71206sw0/3WLsuOPDYQ1lRimDhs57WARqa2mzsli76O9AExXwvuPBP6HH
         K47myiF169lwluDToZvaNYdLilNHvny6JD/JcIWthnILtnTDMjjzQf4WXXO9QFh06o/G
         bcUHHDPXkkN+4777s7VuM1awRpt4rzrE1d2vRialE++fEn5LSAboNh8g7yZ9zvlykyID
         V6pLMfVXHWaQdTdhgFDi/bUlVoJkqscGA1YVtHgyRY+vEJPzTgf60LHYV/zAtaVAeWQa
         O4UOM5u4lD8c1woDJywU1n6JpO99TI1sjcalcfORbF/mniDfcz+16HvxFwUG1AecEOxI
         6bwg==
MIME-Version: 1.0
Received: by 10.49.104.65 with SMTP id gc1mr1327542qeb.22.1351846482769; Fri,
 02 Nov 2012 01:54:42 -0700 (PDT)
Received: by 10.49.107.231 with HTTP; Fri, 2 Nov 2012 01:54:42 -0700 (PDT)
Date: Fri, 2 Nov 2012 14:24:42 +0530
Message-ID: 
Subject: JPEG
From: Sumudu Lansakara <*myemail*@gmail.com>
To: *** *** <***@***.com>
Content-Type: multipart/mixed; boundary=047d7b5dbd946575d304cd7f495f

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EDIT

I found that i can't sent any *.exe by this method. Recipient always reject them. Hope there'll be some solution!! (without using any third party app..)

Answer

A simple solution would be to zip the exe file and encrypt it by locking it with a password. This should keep most spam/virus prevention systems from making out that it contains a .exe file