I just answered the question as it was asked, which as stated seemed to have nothing to do with either IE 11 or Outlook mail. Don't know what other kind of answer you were hoping to get. "Shutting down" the computer certainly means that no virus/malware can get in or out...so your computer is safe. That's what you asked.

The attraction of IE alternatives, especially 5 years ago and more, stemmed more from how clunky IE was rather than the superiority of the others. Firefox/Netscape/Opera were ok and worked fine, IE was awful. The decision for what best to use was easy, though much of Corporate America stuck to IE for employees' internal use. Today, I think IE has done a lot of catching up. I find it pretty decent and comparable to the others though I don't use it as my default browser. OP, there are a half dozen or more solid browsers to choose from, all have there own peculiarities, problems and features and all are free. There's no need to persist with something that isn't working for you.

The below page has some fixes for the main problems of ie11 win7; In your control panel, do you have a TroubleShooter for 'Internet Explorer Performance" run that. Here is a link that might be useful: http://windows.microsoft.com/en-us/internet-explorer/ie-crashes-stops-working#ie=ie-11-win-7

The setting is in IE version 10 & 11. Mine is version 10. By its default setting, the Enable Protected Mode should have already set. To check, open IE. Under "Tools" (top menu), select "Internet options". Under the "Security" tab, you will see "Enable Protected Mode". This should be checked. You can also disable the Flash Plugins. This bug won't work with Flash plugins disabled. To disable, open IE and go to "Tools" and select "Manage add-ons". Under "Toolbars and Extensions", you will see to the right "Adobe Systems Incorporated". Under this, "Shockwave Flash Object" is listed. When you select this, you will see a "disable" at the bottom. Click on it to disable; then, select "Close" to get out of the setting. Doing both, you can continue to use IE.