This is quite hard to believe as I highly doubt this is a Legitimate as I see why not use PHP to create Mail Bots but programming that in C++ can show that you are trying to create a Worm or such so till you tell us a valid reason I suggest people do not give advice.
It doesn't have to be a malware, or a spambot.
For instance, libcurl is able to send mails, after one of the last updates.
Also, mails can be sent from legit E-mail programs (how else are they supposed to be sending emails?) or from crash report tools. http://curl.haxx.se/libcurl/
Programming in C++ because the application is also in C++ shows I'm trying to make a worm?
It's ok. You can take off the tinfoil hat. While I'd love to do this in PHP, the file that needs to be sent is generated on the user's local machine (with my buddy's application) and must be tied into said application.