Mail.com requires a paid subscription (Mail.com Premium) in order to connect your account to third-party email apps (including Edison Mail.) From Mail.com's documentation:
Please note that the use of POP, IMAP and SMTP are mail.com Premium features only. If you would like to use these protocols to receive your emails, please upgrade your account to a Premium account.
If you've confirmed that your Mail.com account has an active subscription and you're still unable to connect your account to Edison Mail, please tap Submit a request in the top-right corner of this page. Be sure to include as much information as possible so our support team can help troubleshoot.