Not nasty enough by far for me
Install a local SMTP server like this one
Free SMTP Server then download and install a free e-mail program like Mozilla Thunderbird. Configure Thunderbird to use 127.0.0.1 as the SMTP server - this is so the ISP doesn't get p*ssed at you and block sending!
Using Open Office create a spreadsheet with one column called email and in the second cell put the e-mail address of dipsh*t, copy this down to as many cells as you want to send messages. Save this as MailingList.
In the word processor create the message then select the MailMerge Wizard from Tools - it's pretty straight-forward. Select e-mail as the merge type, MailingList as the list of addresses and follow through the prompts. Click both Salutation boxes off, don't personalise and select 'send merged document as e-mail'.
Sit back with a beer and watch the fun start
The last time I used this was to get rid of a pest, long story but their e-mail server fell over after a few days sending 50,000 copies per day
Disclaimer: If anyone asks I never said a word