Thanks for the suggestions.

The query came about as I had discovered that I could keep a MAIL folder on both the desktop and portable. Then before a trip use GoodSync to get the portable MAIL folder synced with the desktop and the first job when returning home was to sync back again onto the desktop. This was a surprise as I expected problems between the two. You explained this  "keep in mind that the configuration files are stored in the mailbox directory and its likely you'll need different settings for the two devices."

As I had got away with it with a simple two syncs at the beginning and end of a trip I thought I would enquire about the repeated syncing that would happen under Dropbox.

Seems I am safer sticking to a system, that so far, has worked for me. 

With Pegasus Mail running under Windows on both a desktop machine and a portable would it be possible to have a joint "Mail" folder in the same Dropbox account?

The Mail folder would be synced each time either machine was booted.
I would take care not to use Pegasus until a Dropbox sync had taken place, or to have both versions of Pegasus running at the same time.

Regards
Tony

I don't think so.  Attempts to maintain a mailbox directory synchronized between two devices has been problematic because the sync process interferes with the routine writing/updating of files.  If you used Dropbox, it could only sync when Pegasus Mail was not running on either device otherwise you'll have problems.  Can it be controlled that way?  Also, keep in mind that the configuration files are stored in the mailbox directory and its likely you'll need different settings for the two devices.

Two options are:

• Use IMAP on both devices.  Mail would then stay on the host server and be available to any device.
• Use POP3 to download messages with one of the devices but configure it to leave mail on the server where it would be accessible to the other device via IMAP.  One disadvantage is no common repository for copies to self.  A workaround is a BCC to yourself when sending from the device using IMAP.  Another disadvantage is that you eventually need to do cleanup of the host server.