To reply to a message, select the message to reply to in the message list and click the Reply button in the toolbar, or right-click within the message and select Reply to Sender. This opens the message composer. The To: and Subject: fields are already filled, although you can alter them if you prefer. In addition, the full text of the old message is inserted into the new message, either in grey with a blue line on one side (for HTML display) or with the > character before each line (in plain text mode), to indicate that it is part of the previous message.

If you are reading a message with several recipients, you can use Reply to All instead of Reply. If there are large numbers of people in the Cc: or To: fields, this can save substantial amounts of time.

Susan sends an email to a client and sends copies to Tim and to an internal company mailing list of co-workers. If Tim wants to make a comment for all of them to read, he uses Reply to All, but if he just wants to tell Susan that he agrees with her, he uses Reply. His reply does not reach anyone that Susan put on her Bcc list, because that list is not shared with anyone.

If you subscribe to a mailing list, and want your reply to go just to the list rather than to the sender, select Reply to List instead of Reply or Reply to All.

The default settings for replying and forwarding can be changed under EditPreferencesComposer PreferencesGeneralReplies and ForwardsReply style.