I have PMail installed with the -roaming and multi-user parameters, and my mail is located in a directory separate from my PMail program directory. I am thinking of moving it to the Dropbox directory, so I can have my mail accessible from both the desktop and the laptop (with the usual precaution of being sure that PMail is closed on the other).
1) is there any known problem associated with this?
2) should I do this from the "general settings / mailbox location tab" in Preferences--where the current installation is given as "<default>"--or should I close PMail, move the file manually, and then do a reinstall of the program, setting the mailbox location through the installation wizard?
3) the Help file refers both to a "main" folder and a "default" folder to which the new mail goes. What are these and how do they differ (as far as I know the "main" folder is just one of many in my folder list).

Thanks in advance for any clarification!

I have never known anyone to have been able to get this to work. Even attempts to sync the local mailbox directory to with a remote location have failed. Pegasus Mail constantly reads and writes to the mailbox directory(ies) and needs immediate and exclusive access.

Edit: I dawned on me that from what I know of Dropbox, there isn't any way to create path to it that Pegasus Mail could use. Pegasus Mail requires a drive letter. I don't know if that is possible with Dropbox. Even if it is, the functionality of is remains a problem

I don't know the context of what you read in the Help file regarding the "default" folder but I will assume that it is where new messages arrive. As each new message arrives it is written to the New mail folder directory as a .CNM file. When you look at the list of messages in the "New mail folder" you are looking at a list created from data found in each .CNM file. The "New mail folder" is unique in this regard. Every other folder is made of of two files, a .PMM and a .PMI file. The .PMM file stores the content of every message in the folder. The .PMI file contains the index of message content location in the .PMM file.

Hopefully, my answers to questions number 1 & 3 make question number 2 irrelevant.

The best way to accomplish what you want is to use IMAP connections on both devices. If POP3 is a must then I believe the best, although not ideal, solution for those who have done it has been to have one device retrieve mail via POP3 but leave it on the server available for the other device to see it using an IMAP connection. A drawback is that copies-to-self sent by the first device will be stored locally so will not be visible to the IMAP device. A BCC to yourself might overcome that but could be difficult to manage.

Thanks for the full (if disappointing) response. Dropbox is just another folder on my PC, easily reached by a normal path. Even in airplane mode I can read and write to it. I suppose the constant synch and Pegasus continuous use at some point interfere with each other.

I try to keep my mail on my local machine, and not in an institution's or company's cloud on the a web, so I avoid IMAP. (Perhaps this is pointless paranoia or distrust.) On my Android I use BlueMail and the "do not delete" option, and periodically erase the mail on the 'phone, but that makes saving replies, as you note, difficult. I was looking for an easy way to go back and forth between the two machines.

On the other hand, there's the solution of using IMAP and even IMAP+POP3. You could access your messages via IMAP while on the go, and POP3 when back at your base. These days, I no longer take my laptop on trips, at most a tablet, so I access my accounts using the web interface or Pmail-ROAM.

Exactly.

I can relate. I do the same. For awhile I had a desktop PC at home and carried a laptop when I traveled. Pegasus Mail was installed on both. I attempted to solve the same problem you are attempting to solve now. I did not find a solution that did not have its own set of problems. I have since done away with my desktop (and home office). My laptop travels with me. Life is just a tad simpler now, although I really miss the functionality and solitude of a desktop PC in a home office.

I remember a longtime Pmail user who had the same problem, Frederik M. Balster-Philips van Buren from Sweden. He traveled extensively throughout Europe, so his solution was to install Mercury in his home office. His desktop automatically accessed his email accounts 24/7, and he accessed his desktop (POP3/SMTP) when traveling, all via Mercury. Don't ask me how, as I've never used Mercury.

Just as another option.
I've used VNC to access my main machine while away.
Have to install the VNC server on the main machine. Will have to open the port on your router to map to the machine.
Default port is 5900, but you can select different ports, and can also use ssl connection that gives more security depending on server. With windows I've used TightVnc and Tigervnc. On linux I use TurboVNC, but it doesn't have a windows server only a viewer.

For short periods, it works fine. For longer periods, I copy Pegasus to my notebook.

So, another option. Have used it with even a dialup 56K connection long ago. Since it only transmitts the screen image from remote machine.

Always nice to know I'm not alone. But if the problem is the conflict with the continuous synching, then is this the answer?: turn off synch in Dropbox during the times I use Pegasus. This is easily done in Dropbox icon in the notification area, and Pegasus is set to do things only when I initiate them. It involves paying attention to the extra step, but that might be worth the convenience of having it on both.

If so, that brings back my second question above.

(I've tried using a separate, USB drive installation, synching the MAIL folder with Total Commander every time I go back and forth, but that is really inconvenient and using the thumb drive is very slow)

I administered a Mercury server for a 15 user business before retiring 5 years ago. Each user had an email address hosted on our domain host. Mercury would retrieve messages via POP3 and distribute them into local mailbox directories. Users could access their messages when in the office by running a shared installation of Pegasus Mail on their desktop PC or, when out of the office, via IMAP with any email client.

Do I think doing this is worth it for a single individual? No. You would use Mercury to retrieve mail via POP3. It would be placed in a local mailbox directory where you could access it with a local installation of Pegasus Mail when at home or by connection to Mercury via IMAP while traveling.

IMO, too risky. There is no way to know what kind of corruption would occur if Pegasus Mail was run while continuous synching was enabled.

This could be a viable option. I have extensive experience doing this. In my case I had a Pegasus Mail installation on a flash drive that I used exclusively for Pegasus Mail support. I plugged that flash drive into my desktop PC at the office, my desktop PC while at home, and my laptop when I travelled. I wasn't just synching a mailbox, it was a fully functional Pegasus Mail installation. I still run it today however it no longer resides on a flash drive. It has been copied to the hard drive of my laptop. It took a little while to get used to dropping that flash drive into my pocket almost every day but it became a habit pretty quickly. I had a script that copied the installation from the flash drive to my home desktop hard drive for backup purposes.

BTW, regarding your question number two, using the "general settings / mailbox location tab" would not accomplish what you want because the default new mail folder would not move. A manual move would not require a reinstall. There is a utility provided with Pegasus Mail named PCONFIG32.EXE that allows you to tell Pegasus Mail where to look for the mailbox directory (ies).

I will accept the wisdom of your advice on the risk. I don't like using the flash drive as the sole program, because of the risk of loss or failure (I've had a flash drive just fail completely for no apparent reason) and because it is so slow (a function of the NTSF file system? I formatted it so that it would correctly preserve time stamps on DST) but I see that I can put an installation directly on the laptop and use the flash drive or local network to just move a copy of the (closed) Mail folder between machines, replacing the old one each time, which is less cumbersome than use a separate synch to replace changed files.

Many thanks for the attention you've given this.