Thank you for contacting us and I'm sorry about the issue you're experiencing. The way our security system works, you should have received the authentication email after you first signed in to your mSecure account the very first time in mSecure 5 on Aug 19th 2017. We have found that for some customers the email gets placed in either a spam/junk folder or some other folder in their email app do to rules set up to automatically route incoming emails. Make sure to run a search in your email app to see if you can find an email from: "firstname.lastname@example.org". Be sure to run a search specifically from inside your spam folder as some apps omit this folder when searching for emails.
Unfortunately, if you are unable to find your mSecure Authentication email, there is no way for mSeven Software to resend it to you. In order to maintain the security of your account, we do not have the information needed to retrieve your account key. The only way to resend the Authentication email is for the owner of the account to resend it from the Account Settings from within the mSecure app.
You can go here to learn how to resend the authentication email on all devices if you still have access to your mSecure account in mSecure 5 on a device: https://support.msecure.com/support/solutions/articles/36000064234
If you have lost access to your Authentication email or access to your mSecure account on a device, you will need to go through an account reset to reset your account: https://support.msecure.com/support/solutions/articles/36000064228