Arbitrary email addresses in send and reply fields

Question

I have been trying to figure this out for a while, so apologies if it seems obvious. I have a domain foo.com and use many different addresses [email protected], [email protected], etc to distinguish mail from different senders. For example, if I set up an account at amazon I give an email address of [email protected] to allow simple spam filtering and categorization. Then I open a gate in mac mail by adding a rule saying allow mail to "[email protected]". All these addresses (and there are MANY of them) are directed through a single account by my host service. Though the "to" field distinguishes them, the account they come in under is associated with an official email address of "[email protected]".
Sometimes I need to send an email from one of these addresses. In particular, certain sites require an email+reply confirmation process which demands that the reply come from the [email protected] address. Often the original is sent via a web form, so mac mail plays no role. In mac mail, I can set the default to reply from a fixed address (from the list of official account email addresses) or from the official address of the "account" I last looked at, etc. I can also select from a pull down list of the official account email addresses. However, without adding a bzillion email addresses to the list by hand (and selecting or changing the prefs each time), I can't seem to simply modify the reply-from address or the sent-from address to be arbitrary. I want to do 1 of 2 things:
1. Easily and directly edit the sent from or reply from field of a single email without changing any default settings or going into a preferences pane.
or 2. Set a default of "reply-from" the address to which the email was addressed (rather than the account).
I imagine the 2nd is problematic because there is no way to identify the address which is "me" in the recipient line if it is not known (like the "official" account address). I know how to do the 1st with sendmail, but that kind of defeats the purpose of using mac mail for integration.
Does anyone know how to do this?
Thanks in advance for your help.
Cheers,
Ken

Answer 1

Thanks for the reply, but that doesn't quite help. I don't want to have to go into preferences and add a new address each time I reply. There are over 100 of these addresses and most get used infrequently. I want to simply edit a field in the email directly. The drop down menu solution doesn't work with a large and constantly growing set of addresses. Imagine you have [email protected] through [email protected] on your domain bar.com. If you get an email addressed to [email protected] you wouldn't want to have to go into preferences and add that to the allowed list before being able to reply. I want to simply reply as [email protected] There are legitimate reasons to set stuff up like this. I just want to be able to edit the "from" field in an email message the same way I can edit the "to" field. It would be equally frustrating if I had to go into preferences to add a recipient's email address every time I wanted to send one out.