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Mail Forward (versiontracker.com)

Then setup your hotmail accounts in mail, but set them not to check automatically (Mail Forward does this), and then to send using your ISP's SMTP server.
 
To use Hotmail with Mail (Or any other POP/IMAP mail program) you have to have the payed version of Hotmail. Then you will be given the information to set up your mail app.

Once you have received all the details:
1) Open up Mail.
2) In the menu bar go to Mail>Preferences.
3) Click on 'Accounts'.
4) Click on 'Add Accounts'.
5) Choose your account type either POP or IMAP.
6) Fill in the black spaces with the provided info.
7) Choose 'Add Server...' from 'Outgoing Mail Server'
8) Enter your SMTP's server details (either from your ISP or Hotmail)
 
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