Exchange can handle mass mailings, but the server will throw all it's resources at the mail to get it out as quicky as possible and you may find the server / internet get sluggish right after sending the emails out as Exchange.
If you have large attachments, you need to calculate how long this will take to send which depends on your outbound (upload) connection speed.
If you have 500 emails with 1Mb attachments, that is at least 500Mb of emails. Down a 512kb upload speed line that will take Exchange approximately 2 hours 50 minutes to send.
Down a 1mb upload line it will take aproximately 1 hour 23 minutes and down a 2Mb upload line it will take approximately 41 minutes.
In terms of being blacklisted / marked as a spammer, you should not get Blacklisted provided everyone you email has opted in to your mailings and you have an option to unsubscribe from further mailings. Blacklisting is unlikely if you have cleansed your database and do not have any honeypot addresses in the list (a honeypot is an email address setup to catch spam that has never been advertised and has been captured by a spammer whilst trawling the web for email addresses to abuse).
