Exchange mailbox may have multiple SMTP addresses. For outgoing messages Exchange server always uses the primary SMTP address.

For example, John Doe has a mailbox with john.doe@companya.com primary SMTP address and john.doe@companyb.com secondary smtp address. John Doe can easily receive the message addressed both to john.doe@companya.com and john.doe@companyb.com, but he can not send the message as john.doe@companyb.com because this behaviour is by design in Exchange server.

ChooseFrom for Exchange 2000/2003 application allows users to send a message with any of their own SMTP addresses as the From address.

• ChooseFrom for MS Exchange 2000 1.1.1
  Exchange 2000 mailbox may have multiple SMTP addresses. For outgoing messages Exchange 2000 always uses the primary SMTP address. For example, John Doe has a mailbox with...

• Star Bulk Email Sender 9.45
  This tool directly sends mass e-mails from your computer

• Mail Storage Guard 1.
  Mail Storage Guard is an extension for Microsoft Exchange 2000/2003 and IIS SMTP servers, designed to protect your mail server from spam, prevents mail relaying, mail bomb and NDR attacks. The protection is realized both on the level of SMTP...