When using the mailing list feature there are a few possible maintenance messages you may receive from your mailing list. However they don't require any action on your part.
Here’s a quick explanation of what they mean:
Subject Line: 'The prospective subscriber address generates the following multigram matches to the current list:'
If someone has recently subscribed to your list you might get this message. This is the mailing list checking for duplicates, you can safely ignore this message as it will take action automatically.
Subject Line: 'You have added to the subscriber list of:'
This is the message you receive when someone signs up to your list. You can simply ignore this.