You can do this if you configure those addresses under Settings, Sending Identities (used to be called Personalities IIRC). It slightly annoying the first time,

You can do this if you configure those addresses under Settings, Sending Identities (used to be called Personalities IIRC). It slightly annoying the first time, but once done, any hitting reply to a mail sent to one of those addresses will already have the appropriate From header set.