Need help from anyone who uses Apple's Mail App in OSX

[Jill Whenmouth]

Here's the problem: my son (the one you all helped me with choices in
setting up his new office, tho we haven't finished that yet)  is having
problems with stuck mail sitting in the Mail outbox.

I don't know Mail, have never even seen it, except what is on
webmail.mac.com which i assume looks like Mail,  because  I am using outlook
express and OS9, and  so I am guessing my way thru helping him. But  I don't
know the details of Mail, so feel way frustrated and know I don't know
enough to solve the problem.

What I would like to do here is tell you what he has told me.  And tellyou
what I have told him to try and what he has done that hasn't worked and what
conclusions we have arrived at.

And then hope that you will have suggestions.

 He is running 10.2.4 on his ibook 900mhz. 128 mgs memory (he has more
memory to install, but that hasn't happened yet.  He has a .mac account
which he is sending from.  He is in cozumel mexico using the cable co as his
isp and thus has hi-speed. (I don't have cable  and so am not familiar with
that, though together we guessed our way thru setting it up when the tech
had failed... but I don't remember any of those details)

What happened. He sent out three emails to three different email isps and
they all sat in his outmailbox for a day and a half, doing nothing.

What i have had him do.... with no success at moving those 3 emails....is

 Quit and restart mail.  Quit and restart the computer.  Drag the 3 emails
out of the "out box" into the "in box" to clear the out box in case it had
jammed in some fashion or got hooked into a loop of send later somehow.

I had him send a test email to himself at his .mac account from himself at
his .mac account with one line of text.  It  went out immediately and
arrived successfully to himself.
 Then i had him send a test email to me at my .mac account which went out
immediately and arrived in my box right away.   Hmm. OK!

Next, he did a Cut n paste of the contents of one of the emails which had
been stuck in the out box,  a  text only message of  two short paragraphs,
into a new email, typed in the sender's email and subject,  and clicked
send.   It sat in the outbox... nada.  We tried the same with the second
email which had previously been stuck in the out box.  Same result - it sat
in the out box not moving.

Conclusion: The emails to .mac accounts go out with no problem.  The emails
to anyone else don't move.

Thinking back, I realize that he has never sent emails out from this account
to non .mac accounts.    All the emails previously sent out had been to .mac
accounts.   Now with his new business starting up, he was ready to send from
his .mac account to other emails for the first time.

 (Oh, oh, do i remember vaguely remember something about our not being
supposed to use mac email accounts for businesses?  Does anyone remember
that?  Well, if so, I will set up a free subaccount using my sbc account.
But I think the same issues of stuck mail using Mail are going to apply and
if he makes this a personal use email,  this still needs to be solved.)

Next, I created on my os 9.1 ibook, using outlook express, an account using
his .mac address. 
 At first I had problems, before I remembered that I had to click on
advanced options and select smtp server requires authentication   and
selected "use same setting as incoming mail server." (If i have to switch
him to an sbc account, can someone tell me how I achieve the equivalent when
we set up this in Mail?)
 I tried sending to non .mac accounts and the mail goes out right away.
Conclusion:   i think i eliminated the faint possibility that the problem
was with his .mac account.

I wondered if his email was configured correctly, but i realized that if his
account hadn't been configured correctly, it couldn't have sent out emails
successfully to  .mac accounts.... receiving from .mac accounts, which it
has.
Conclusion: the set up of his account on his computer is configured
correctly.

So why is the non .mac mail sitting in the out box and not going anywhere?

Any ideas?  Cuz I am stuck.

Thanks, Jill