If these are accounts in two separate mailboxes, all you need to do is display the From field and put the address of the second account there when you want to use it to send from.

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Sue Mosher, Outlook MVP
Author of Configuring Microsoft Outlook 2003
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>I have two exchange email accounts set up in outllook2k3 corresponding to two
> email domains set up on my SBS server (ex: dave@a.com and dave@z.com).
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> choose which email account to send from?
> Thanks