How can I reply to e-mails forwarded to my main e-mail address?

Question

Hoping somebody can help.
I've been assigned an e-mail by an organisation I do voluntary work for occasionally ([email protected]) which is set up so that any e-mail sent to that address forwards to my main MobileMe e-mail address. I would like to be to reply to any e-mails received so that the 'from' field shows this same e-mail address.
I've tried to add it as a new account in Mail, however Mail tells me that I can't leave the 'incoming mail server' blank (which I obviously don't need) and so this isn't possible. As a workaround I tried writing 'nomail' here which at least enabled me to set up the account, however the downside is that Mail is now constantly reporting that there's a problem with this account (permanent warning triangle next to my In box) which is irritating.
So my question is, is there a neater way to answer this kind of forwarded e-mail account? I know these kind of accounts are quite common so Apple must have considered this!
Many thanks
Charles

Answer 1

The answer is more or less what you seem to have done, with a couple of added refinements. Set up a new account in Mail; give the Email address as that of the address in question. Enter any old garbage in Incoming Mail Server, User Name and Password, and set Outgoing Mail Server to use your ISPs server - this seems to be qhat you have done and is working - I assume you can send OK?
Now click on the 'Advanced' tab. Check 'Enable this account' (should be done already); Uncheck 'Include when automatically checking for new mail'. This will stop the error messages unless you manually get mail from all accounts.
Now in Mail Prefs click on 'Composing' in the toolbar. Set 'Send new messages from' to 'Account of selected mailbox'. This should recognize messages which have been forwarded from the other account and automatically set the 'From' address to the correct one (you can also do this manually from the menu in the header bar of the new/reply message pane).