That is because E-mail WEB sites such as HOTMAIL (now called OUTLOOK) or GMAIL and so on.......use secured socket layer (SSL) and other security checks before you are able to login into your E-mail account.So for example once I am logged into my HOTMAIL account,the following link is showed in my address bar (this is just an example):
https://dub119.mail.live.com/mail/InboxLight.aspx?n=2328323559878
However if you are not logged into your E-mail account,when you copy and paste that link in the address bar,it will NOT work because the E-mail WEB site (such as hotmail) needs to pass the special login procedure all over again such as checking wether your E-mail address and password are valid,pass the decryption process,SSL and other security checks BEFORE EVEN BEING ABLE TO LOGIN.
And also you CAN save the WEB page from IE when you are in you E-mail inbox,but if you later try to open that file with IE (or other WEB borwser),it will NOT work because of the reason I wrote above.
And that's GOOD because on that way it is a LOT harder for someone to steal your E-mail account.
So if you want to save your E-mail messages locally on your hard disk drive (like I do it),I recommend you to use simple software for that such as Microsoft Outlook Express.With it you can actually download your E-mail messages FROM the server and store them on your hard disk drive locally and (at your choice) you CAN or YOU DON'T HAVE TO leave the copy of those E-mail messages on the server too.
And with this way you can open your E-mail messages (files) locally from the hard disk drive directly without the need to use your WEB browser and without the need to write the LOGIN INFORMATIONS every single time and without the need to save ANY WEB page files from your IE or other WEB browsers and later having difficulties opening that.
NOTE: If later you want to read some of your older E-mail messages,you CANNOT use other computer and simply login into your E-mail account and READ OLDER E-MAIL MESSAGES on the server since the E-mail messages have already been DOWNLOADED on your other computer's hard disk drive locally UNLESS if you have decided to leave a copy of those E-mail messages on the server TOO.That option is usually located in the program's E-mail client itself such as Microsoft Outlook Express.Here is an image:
Cheers!