How do spammers spam?
Richi published a great introduction on how spammers actually send the millions of spam mails every day. He begins the introduction by explaining that there are two dominating ways to send spam emails. traditional and viral
The traditional sending occurs either from local broadband connections, often by using bot nets, that is computer systems that are under the control of the spammer, or even from server farms. Sending out 10 million spam mails that have a size of about 100 Gigabyte in total takes up to five hours on a T3 connection for instance.
The viral spammers use trojans and malicious software to infect computer systems of Internet users to turn the systems into bots that they control to send out the spam using the local connection.
It is easy enough to push out a huge number of emails in short periods of time. While individual server connections may be sufficient, distributing the load to multiple computer systems or servers has the advantage that blacklisting becomes more difficult, and that the sending is even faster.
You might have heard that the Dutch police recently captures three spammers who infected up to 1,5 million computers.
Update: So called bot networks are still a huge problem on today's Internet. Using zombie PCs is a cost-effective way of sending spam messages to billions of users. Users new to the concept of Botnets should read the Wikipedia article on the topic for information on how botnets operate.
The Redtape Chronicles published a 3-part series about botnets that makes another good read. It consists of the three parts "Is your computer a criminal", "Virus gang warfare spills onto the net" and "Who's behind criminal bot networks".
It is a long read but well worth the time if you are interested in the topic.
Botnets back in 2007 were often between 50k and 70k PCs strong. The operators leased out the computing power of their network to spammers, often making $5000 or more per day in the process.
Botnets in recent years have grown considerably in size. The Conficker botnet for instance was said to have control of up to 10 million infected machines.
Malicious software is usually used to recruit new PCs into the botnet. This may include exploiting browser or operating system vulnerabilities, or by embedding viruses into legit software that users install on their systems.
It is imperative for computer users to have proper protection on their system, at the very least a real-time antivirus software, and a hardware or software firewall. Additional tools such as Microsoft's EMET or a second-opinion scanner such as Malwarebytes Anti-Malware Free do not hurt either.

You said that Outlook isn’t your main email client, so which is your main one?
I think its thunderbird
It is Mozilla Thunderbird.
Awesome! This actually solved my problem… what a stupid bug.
If this is the same bug that I’ve encountered, there may be another fix: (1) hover over open Outlook item in Taskbar, cursor up to hover over Outlook window item, and right-click; (2) this should give you Restore / Move / Size / Minimize / Maximize — choose Move or Size; (3) use your cursor keys, going arbitrarily N/S/E/W, to try to move or size the Outlook window back into view. Basically, the app behaves as though it were open in a 0x0 window, or at a location that’s offscreen, and this will frequently work to resize and/or move the window. Don’t forget to close while resized/moved, so that Outlook remembers the size/position for next time.
THANK YOU Claude!!! I could get the main window to launch but could not get any other message window to show on the desktop. You are my hero!!!!
Solved my issue! 6 years later and this is still problem…
Fantastic. Thank you. Size did the trick.
This solved my Outlook problem, too. Thank you. :)
Thank you so much, this started happening to me today and was causing big problems. You are a life saver, I hope I can help you in some way some day.
You are a god – thank you!
thanks a lot…. work like charm.. :-)
Yah…thanks Claude. I’ve been having the same problem and tried all the suggestions…your solution was the answer. It had resized itself to a 0/0 box. Cheers
Excellent post. This had me baffled even trying to accurately describe the problem. This fixed it for me.
Thank you
Thanks a lot for the article. Don’t know why it happenend, don’t know how it got fixed, but it was really annoying and now it works :-)
Thanks a lot. I was facing this issue from past 3 week. I tried everything but no resolution. The issue was happening intermittently and mainly when I was changing the display of screen ( as i use 2 monitors). The only option i had was to do system restore. But thanks to you.
I’ve been tried to sole this problem for 12hours. Your comment about changing the display of screen helped me a lot!! Thanks!!
Thank you…don’t know why this happened but your instructions helped me fix it. Running Windows 10 and office pro 2007
Great tip! Thanks!
Worked for me, too – thank you!!!
It’s Worked for me, too
thank you very much!
I had a similar issue with Outlook 2013 on Windows 10 and this helped me to fix it. Thank you very much!
Thank you so much. Solved!
Considering you published this in 2012, incredible not been debugged by Microsoft.
Thank you again. M
This problem was faced by only one user logging to TS 2008 r2 using outlook 2010.The issue was resolved.
Thanks.
Great tip. Thank you!!!! If it helps, I had to use the Control Key and the arrow keys at the same time to bring my window back into view. Worked like a charm.
Thank you, this worked !!!!
Man, you are a fucking god. Thanks a lot, what an annoying bug!!
Awesome, this post solved the issue. Many thanks!