While you specify addresses of the To: and Cc: field for a new message by yourself, addresses are automatically prepared for a reply message.
For a reply message, Mew prepares addresses for the To: and Cc: fields according to the following rules:
If there are multiple entries for a certain address, they are uniquefied. Your addresses are automatically removed. Addresses ended with ":;", which stands for anonymous recipients, are automatically removed.
You can customize which fields are copied in the case (1)-(6) with the following variables:
If you want to reply only to the address specified by Reply-To:, configure as follows:
(setq mew-replyto-to-list '("Reply-To:")) (setq mew-replyto-cc-list nil)
If `a' or `A' is executed with `C-u', From: of the message to be replied is copied to To:, and Cc: becomes empty. You can use this to reply the sender only.