If you go to https://groups.io/helpcenter/manual/generalinfo/general/bounce_handling.htm you will see their application gives administrators the ability to send a "bounce probe" email to a member whose email was put on their bounce list. If the member replies, it is automatically removed from their bounce list -- without having to ask the user to send an email then having to forward over to tech support like we have to currently do with MailPoet. From that page "The overall bounce handling process in Groups.io is:

Step 1: On receiving a bounce for the first time, the system tries to determine—through a combination of the type of bounce and the frequency of the bouncing—whether the account is bouncing often enough and seriously enough to require action.

Step 2: If action is required, the system sets the account’s status to Bouncing, stops sending group emails to it, and begins trying to reach the account holder via bounce probe emails notifying them that the account is bouncing.

Step 3: If the account holder:

Responds to one of the bounce probes: The account is taken out of bounce handling and goes back to normal.

Does not respond to any bounce probes within a certain period of time: The system sets the account’s status to Bounced and stops sending emails of any kind to it.

When an account is Bouncing or Bounced, the system takes these actions:

Logs entries in the activity logs of all the account’s groups stating that the account is bouncing, to inform group moderators.

Displays a blue B (for a Bouncing account) or a red B (for a Bounced account) next to the account’s email address in the member lists of all its groups.

Includes the account in the “Bouncing” member lists of its groups. (The account continues to appear in the regular member lists as well.)

The affected members are notified by email that they are Bouncing or Bounced. They are also given a chance to “unbounce” their accounts through a special page at the Groups.io site whenever they are logged in.

! Important: Group owners and moderators cannot do anything to “unbounce” members’ accounts. Members must address the underlying problem themselves."