First, you'll get a message that the connection's been interrupted.
This article explains why you might sometimes receive what appear to be chat messages in Yahoo Mail.
Limit for conversations . Maximum conversations allowed in Yahoo Messenger. You may have up to 100 separate conversations at the same time.
When you're chatting with a friend, you can send a graphic to show how you're feeling. These graphics are called "emoticons," because they enhance your words with emotions. For example, when you type this:
A Messenger List is a list of your co-workers, friends, family, and associates who also use Yahoo Messenger, Yahoo Chat , or Yahoo Games. You can send an instant message to anyone on your list, even if they are offline. You can have up to 100 Yahoo IDs on your list.
If you have archiving enabled, you can retrieve your Yahoo Messenger conversation history from Yahoo Mail. While it's not possible to directly download your conversations , you can copy and paste them into a text file or Word document. Save your conversation history
If you are signed in to Yahoo Messenger and open your Yahoo Mail account on the same computer, Yahoo Mail will detect that Messenger is running and it will not load the chat module. However, if Yahoo Mail is opened on a different computer, the chat module will still load. Yahoo Mail will then sign you out of the Messenger client.