The unsubscribe via email does not use the correct email address. I have "myname"@gmail.com but when I send a test it adds this strange email address firstname.lastname@example.org as the email address.
in order to use civimail, you need to have your own domain name for to manage the bounces, and it's the same address used for the unsubscribe (it adds to the address that weird u.xxx string that you see to be able to distinguish between your contacts who is actually unsubscribing or bouncing, it's called VERP).
It doesn't use any of your "normal" mailboxes, it needs a dedicated one to handle automatically bounces and unsubscribe.
For what I see, you haven't properly set-up your email account in civimail and use a gmail address (and didn't fill the local part)
It sounds like you haven't set up your email system correctly. This is the sub-address part of the email but it is missing the local part.
Go to Administer > CiviMail > Mail accounts and set 'local part' to be 'myname+'.
See the manual for more details: Email system configuration