开云体育

Frances,

Groups.io wouldn't allow me to change the email address since it said
that I already have that "proposed" email address in use.

Yup. Managing multiple email addresses is one of the weak spots in Groups.io. That's on the radar, but not promised on any schedule.

So, how do I delete a couple of email addresses that I had used for
testing or as email aliases - there are no subscriptions assigned to
these addresses.

Log in to each address and use the /deleteuser page:
/deleteuser
There isn't a link to that page anywhere.
/g/beta/message/7300

Make sure you've logged out of your main email address, you don't want to accidentally delete the wrong address.

The easy way to log in to these test addresses is to use Email a link to log in. That saves the effort of establishing a password only to delete it.

I don't seem to be able to do that even though I am owner of the sites.

Your ownership of some groups has no bearing on deleting a user account. That can only be done by the owner of the account (which you prove by logging in).

Shal