Rated 4 out of 5 stars
Unfortunately, I can't edit my previous review, the one titled "I can't make it work."
The problem seems to be that the option to upload on program close doesn't always work. I've seen this with both Macs and Windows systems.
If you make changes, you need to remember to upload the file manually or set the add-on to upload every few minutes.
Overall it works -- just not as reliably as I would hope.
Rated 2 out of 5 stars
I created an FTP account and set up the desktop computer to save the file there on exist and load on startup.
A manual upload placed the file as expected.
Then I closed the desktop instance of Thunderbird and opened the instance on a notebook.
After installing the add-on there, I ran a manual download and received the files from the FTP site. Looks good so far.
Next I added a new address on the notebook, closed Thunderbird, and moved back to the desktop.
The new address is not present on the desktop even if I do a manual download.
I presume that I'm missing something that should be clear, but until I can figure it out, I can only go with 2 stars.
I then tried this the other direction. After creating a new address on the desktop, I closed Thunderbird, re-opened to confirm presence of the new address, and closed again. The timestamp on the FTP server shows that the files have been updated.
On the notebook, the add-on reports "copied" and the new address is present.
I updated the new address on the notebook and exited Thunderbird. The timestamp on the FTP site was not updated. (The notebook is a Mac and the desktop is a Windows machine, not that this should make a difference. The Mac never displays a message when Thunderbird is closing, but the Windows machine does.)
After re-opening Thunderbird on the notebook, I manually uploaded the file and observed the timestamp change on the FTP site.
I then closed Thunderbird on the notebook and opened it on the desktop. The status message displayed "copied". The information from the test record has been updated, but the first test record created on the Mac notebook is not present on the Windows desktop and is absent from the notebook.
CONJECTURE: Thunderbird on the Mac does not update the FTP site on close. To maintain synchronized status, the user must remember to push the file to the FTP site manually if changes are made on the Mac version of Thunderbird.