List Owners & Moderators FAQ

Yahoo removing bouncing members after six months

Yahoo is now removing bouncing members who have been bouncing for more than six months (well, that's what they say, but nothing's perfect so you may still find members who've bouncing for longer than six months that haven't been removed).

From Yahoo! Help - Groups Members - Removal of bouncing email addresses:

Yahoo! Groups will periodically remove email addresses which have been bouncing for long periods of time. If Yahoo! Groups determines that an email address has been bouncing for more than 6 months, we may remove it from our system. An email address is said to be bouncing when it consistently returns messages as undeliverable and is therefore determined to be inactive.

There's a "more information" link there which leads to Yahoo! Help - Groups Members - What are "bouncing" members? which explains what bouncing members are and about the "test messages" aka automated reactivation requests that Yahoo will send periodically.