These days, AOL mail users are going through Outlook mail application issues. Generally, it happens because of the IMAP or pop3 server settings. Here are the guide to fix the problems.  you can simply apply it on your device to find the solution. 

mail was unable to open this mailbox on the server “imap.aol.com”.

How To Fix AOL mail not working on the iphone or computer problem? 

• When AOL mail is not connecting to the outlook application, you need to check the internet settings. most probably, something is wrong with the user account or password.
• Go to the account settings, here you need to click on the imap settings. here you need to click on the imap and pop3 servers. Now update the imap and pop3 mail servers. they both should be working fine. 
• Let's delete the current account and then re-add the mail account on the phone. now re-add the mail account on your phone. 
• If imap aol mail not working on the outlook application. you need to check the security settings on your pc. most probably, the firewall is not working fine. so you need to remove the current account and then re-add the mail account on your phone. 

Once you will make these changes inot the aol mail account. your mail application will start wrokign fine. for more details, you need to visit down reporter blogs. there you will find the complete guide.