Because I work fr om different computers at different locations, I have my mail directory on an external harddisk, which I plug into whichever of two computers I work on. This has so far been a hassle-free way of dealing with the problem of using the same email setup on different computers. Recently, however, messages downloaded on one computer have started not turning up on the other and vice versa. It is as if The Bat thinks I am two different users using the same message base and it filters the in and outboxes depending on which computer I work from. Some folders (actually only some of the primary inbox folders) show up as empty on one computer and filled on the other.

I am 100% certain that both computers are using the same message base. I have a feeling I have inadvertently run into a downside of an otherwise clever feature. Either something with encryption or something with multi-user functionality that I know nothing of. Does anyone recognise this? I opened a support ticket, but I'm pretty desperate so asking here too.

Setup: One desktop running Windows 7 and one laptop running Windows 8. I use seven email addresses, all hosted by one.com, some of which are fine, some of which give problems. I have upgraded to 6.0.12 and this may well be wh ere the problems started but I am not 100% certain. I downgraded to 5.4.0 again but no luck. I have tried changing permissions as I saw these were different for different message bases. No change.

I have considered viruses and done clean Windows installs on both computers. No change. I have moved the entire mail directory structure away from the external harddisk and onto both computers. No change.

Any help much appreciated.