For Mozilla Thunderbird Users:

1) Go to Tools --> Address Book

2) On the left section, click Personal Address Book --> Look for listmgr@plaympe.com and delete it.

 

For Microsoft Office Users:

 1) Under Home Section, Go to Address Book

 

2) From the list of contacts, look for listmgr@plaympe.com. Right-click on that entry and choose delete.

3) Click Yes to complete the process.