The sender's name is included in the Address list when you click Reply All to a message that is stored in your Sent Folder or in your Sent Items folder on an Exchange client

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Messages that you receive from other people have your identity stamped on them by the transport. On a reply or reply all, the Exchange client always puts the sender's name in the address list, then uses your identity as found in the original message to strip your name from the address list. Messages in your Sent Items folder do not have your identity because they are dropped in the folder by the spooler and do not pass through the transport. Therefore, the sender's name (yours) is not removed on a reply-all message.

Steps to Reproduce

1. Compose a message to someone other than yourself and send it.
2. Go into the Sent Mail folder and Reply All to the message just sent.

The sent message will contain the address of the sender.