Each mail account folder has pairs of files, like the Inbox and and Inbox.msf, Sent and sent.msf. The files
without the .msf extention, i.e. Inbox or Sent contain the e-mails, and should not be deleted.
Files like Inbox.msf and sent.msf can be deleted from the hard drive profile location, and your program closed. On reopening the program the .msf or "header" files are rebuilt on the basis of the file with no extention. sometimes the .msf become corrupted, and should be deleted. So, obviously, no mail is lost, if only the header files are deleted. E-mails can be blank, and, they are, usually, spam. That should be given away by the Subject and sender, although at times even the subject is blank. It is not common, but they come in bunches. Best way to verify what they are like is to highlight that message, select View|Message source. That will give you e-mail address, and other useful information. I would say, delete the .msf files whenever in doubt, but first Compact the folders.
When an e-mail is deleted is not completely removed from the Inbox. Compacting will remove those already deleted e-mails. I do that all the time, and more than once a day, and my mail has been ok. However, if there had not been any compacting, there may be long delay. In general, not compacting is pretty deadly. I suppose that you could back up the files, but if he has a lot of floating no good mail, you would just do that, back up garbage.
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