Send only email accounts and Mail.app

[Robert L. Vaessen]

All -

I've often been frustrated by attempts to create spoofed email accounts 
with Mail.app.  Perhaps someone could explain a procedure which will 
not cause errors.

I would like to be able to compose and send an email using a 
From/Reply-to address that is different from any other email account, 
yet has the same incoming/outgoing server settings as other accounts.  
I have some email addresses that are forwarding addresses only.  Mail 
to those addresses show up in a standard POP configured email account.

When I try to create email accounts that use the same receive/send 
settings as other accounts, but different from addresses, I often 
encounter errors.  The only difference these accounts would have is the 
Description, email address, and Full name settings.  How can I 
configure an account in Mail.app to have the same incoming/outgoing 
server settings without creating errors?

Example 1:  I own the domain RobsWorld.org, I would like to send email 
from robert at robsworld.org, or dungeonmaster at robsworld.org.  I can 
create the first account with no problems.  However, when I create the 
second account I get error messages.  It seems that I am not able to 
use the same incoming/outgoing server settings as the first account, 
while having a different email address setting.

Example 2:  I have an email forwarding alias. The email to that address 
shows up in my pophost.com Inbox.  I would like to configure an email 
account that uses the forwarding alias as a from: address, instead of 
the pophost.com address, while still using the same incoming/outgoing 
servers.

It seems that the folders/files created on the computer when email 
accounts are created, are named according to the incoming or outgoing 
server names.  Is this correct?  If so, how can I get around this 
restriction?  I'd like to be able to select one of several different 
From: addresses from the compose windows pull-down account setting.  As 
in send using a specific smtp server, yet select a different from 
address than the one normally configured for that server.

Currently, I am able to do this, sometimes..  I'm not sure what the 
correct procedures are, or whether there is an easy, error proof way to 
do this.

I'm not trying to forge/falsify anyone else's identity, or create fake 
headers.  All the email addresses I'm working with belong to me.

Any help would be appreciated.

- Robert