Blocking an email on your Optonline email account will cause the email to be automatically deleted when it hits your inbox.
It will never appear in your account when you look at your email account.
To block emails on Optonline follow these steps below.
Once in your Optonline email account, Click "Preferences" in the upper-right of the screen to view the management options for your email account.
Next Click on "Blocked Sender List" and enter the email address you want to block in the appropriate field. Click "Add."
Next Click on "Delete" or "Spam Folder" to indicate where you want the blocked emails placed.
And last Click on "Save" to keep your new settings for the email account.
That should block emails on your Optonline email account.