Sometimes the browser will get confused and tell you that you already have a session in use or another type error that means the cookie isn't working correctly. The best way to handle that is to clear the cookie that our site has stored in your browser. We do have instructions for other browsers located at this link.
Please follow these instructions for Microsoft Edge. There are images below if you would like to refer to those.
Here's specifically how to clear your cookies for our webmail's website at https://email.iljmail.com
Go to the website that is showing the error (in this case, it's email.iljmail.com)
Click the secure symbol padlock icon to the left of the web address near the top of the browser.
Select Cookies and site data.
Choose Cookies
Click where it lists the website to select it
Click Remove at the bottom of the pop up screen
Click Done
Then refresh your browser page and try to log in again.