Talking about email annoyances, a few days ago one of our computers got a big problem: Microsoft Outlook crashed repeatedly with a mysterious ntdll.dll error.
Rebooting, re-installing Outlook, installing a myriad of Microsoft patches - all failed to solve the problem. At the time, scouring Google for this particular problem didn't help: there was no helpful hint on how to solve the problem.
Here's how to solve it: turns out it was a Cloudmark spam filter (plugin) installed on that particular computer - we had to uninstall the software manually (some people said that all they had to do was rename this folder: c:\documents and settings\YourUserName\Local Settings\Application Data\Cloudmark into something else like ...\Cloudmark-Bad).
After close to a year of trouble-free service, the Cloudmark people did something dumb: they did an automatic update that contained a bad bit of mojo. And the terrible thing is CloudMark's website had no clear announcement of the problem (and when they did announce it, they buried this bit of bad news in the Download section - and this news is gone as of today!)
Moreover, CloudMark never sent us any email alerting us of this problem (we have other computers without the software that can get emails fine. Of course, logically, if that's your only PC then you have to use another email client to fetch your emails).
Grr! Bad Cloudmark! Bad!