Multiple POP3's, and which SMTP...??

[pawhe]

(Outlook 2002 SP3)

Had one (dial-up) ISP, (ISP 1) therefore one POP3/SMTP account (default)
configured. No worries.

Now got ADSL. Have created a new account for POP3 for new ISP (ISP 2), and
set this to default - mainly so that the SMTP server used for outgoing is
the new ISP's not the old (as trying to use the ADSL line to SMTP connect to
the old ISP fails, as it seems that the old ISP won't allow SMTP connections
from networks outside theirs - this is standard practice to help restrict
SPAM?).

So, create a NEW email, click on send, and the Outlook dialogue box shows:
"Receiving on ISP 1.......COMPLETED"
"Sending on ISP 2.........COMPLETED"
"Receiving on ISP 2.......COMPLETED"

BUT, as far as I have been able to ascertain, if I "reply to" an email that
was received [directly into] via the ISP1 account, when I click send it
shows:
"Sending on ISP 1 .... .....FAILED"
"Receiving on ISP 1.......COMPLETED"
"Receiving on ISP 2...... COMPLETED"

So, the question (finally!) - why does the Outlook to try and SEND the
(freshly created) reply email via the ISP 1 SMTP servers - why isn't it just
using the settings from the new DEFAULT account (ISP 2), and trying to send
via ISP 2 SMTP servers???

Any workaround for this, as whilst I'm transitioning from ISP 1 to ISP 2,
looks like every time I want to reply to an email received via the old
account (POP3), I need to actually create a "NEW" one, and copy/paste
anything I want to quote, or in fact the originators email address, into the
new email.... a right royal pain..!!

Thanks,

P.