Sending mails via Java (using Java Mail API) requires you to setup an SMTP host that would send your email to the recipient after proper log-in validation. I've used Java Mail with Gmail IDs and Gmail as SMTP host server. Some e-mail service providers do not allow sending emails from outside of their own web-services (making them incompatible with Java Mail).
But, in order to support multiple senders, you'll need to do the following:
- Change the SMTP server to your correct host as per the email ID in use.
- Run the Authenticator, with the new e-mail address and password, every time the sender ID is changed.
- Then send your message.
My suggestion would be to store these sender email IDs and passwords (and SMTP hosts) when the program is initially run and then iterate the above steps with required changes, for each email id and password pair.
The Caveat:
In my opinion it's best to stick with a single sender else, multiple messages with similar content, by varied sender addresses, may be marked down as Spam by the recipients email service provider.