Okay, I've run into a number of email attachment issues in recent weeks. Most have been resolved, but there are a couple that could be causing your problems.
The first is: the device OS version. Email attachment handling does not work correctly with any 4.5.0.X device OS, where X is less than 52. In addition, I found that email attachment handling also did not work with the 4.3.0.Y version that Sprint released with its BlackBerry 8330; I do not recall whether simulators had the same issue, but it wouldn't surprise me. Simulator versions track the device versions; no BlackBerry 4.3 device OS correctly handled email attachments, and no pre-188.8.131.52 device OS correctly handled them either, so my guess is no 4.3 simulator and no pre-184.108.40.206 simulator will handle them correctly, no matter what.
Second: until last Sunday, BIS-based email transmissions were broken when it came to delivering email attachments. Any device associated with a BIS (BlackBerry Internet Service, basically an email address that looks like
, etc.). That problem was fixed as of this past Sunday, so BIS devices should be reading email attachments correctly at this point (and the device OS version didn't matter; 4.2.X devices were failing email attachment handling until the BIS services were patched over the weekend).
Now, assuming you're not using a 4.3 simulator, and assuming your email service simulator (ESS) is set up correctly, email attachments should get delivered to your application running on the simulator. However, there are a few quirks to setting up the ESS. In the "BlackBerry Email and MDS Services Simulators 4.1.2\ESS\help" folder is a document called "Using_the_Email_Server_Simulator.html" which provides an explanation of how to set up the ESS - I've gotten it to work by giving it my work email access (we use Outlook) parameters (server name, username, password) and it effectively becomes a bot that polls my corporate Exchange server for email and delivers what it finds there to the BlackBerry simulator, attachments and all.
You will likely want to try the "Load Test" which will attempt to load (into the ESS) all the email currently available from the mail server that the ESS is pointed to. This may take a few minutes to get working, but you should see a list of all the email available on the server. I didn't normally need to do this, but it's a good way to check that the ESS is communicating properly with the email server it's supposed to be polling.
I have not yet been able to get the BlackBerry simulator to transmit
email from the simulator to a real email account. Since I haven't had a serious necessity to do so, it hasn't been a priority for me to figure out how to do that.
Beyond that, make sure that the attachment filename is prepended with "x-rimdevice". It's not altogether clear that this is required for device OS 4.3 and later, although it's not altogether clear that I'm mis-remembering something (it happens every once in awhile). Certainly, that's how it used
to work, and if it's no longer necessary, it doesn't hurt.