I use a lot of email addresses for myself, to try to limit spam and separate personal contacts from commercial contacts. I have about 200 email aliases, all of which are forwarded to my main inbox. It would be most useful if there was an option to, when I reply to a message, use the address to which the original message was sent as the from address in the reply.
For example, if I receive a message from Home Depot to the address that I set up for them, e.g., HomeDepot@mydomain.com, and I reply to the message, the same address becomes the from address in my reply.