Copy the Thunderbird folder from one computer to the other:

https://support.mozilla.org/en-US/kb/moving-thunderbird-data-to-a-new-computer#thunderbird:linux:tb60

I have already created a new profile. How do I merge the two (actually three or four)

If you just want to copy the mail from the old setup, use ImportExportTools:

http://kb.mozillazine.org/Importing_folders

The addon is incapable of fixing disjointed folders

rv_hochhalter said

The addon is incapable of fixing disjointed folders

Thunderbird does not have the ability to merge folders of mail successfully without manual intervention.

Thanks for the attention but that doesn't help. What is the intervention required?

You should import the mail folders from the various profiles into Local Folders in the new install, and then manually move them into the desired folder structure. Do not attempt to move large numbers of messages into IMAP folders. There is no facility in TB to automatically eliminate duplicates, although it should be sufficient to sort messages by Subject, Date etc.

The good news is that I can see my old stored emails by text editor (can anyone say security?), the bad news is that the more I work on this the more disjointed everything is getting. I'll keep working on it.

Security is an interesting thing. text or a proprietary binary format that everyone knows? No difference at all in real security, only in preventing casual snooping. Although casual snoops will just fire up a copy of Thunderbird, it is a whole lot easier to read the mail in it. On linux it get even more interesting as most applications are open source and their data structures and file formats are easily determined from the source code. So do not be mislead into thinking using a storage format other than text is more secure. Security through obscurity is a fallacy.

What most people miss is that security is provided by the operating system, as is file system encryption. On a Linux system the only ones with access to your data are yourself with your password and those that possess the root password.Screen locking is not an issue and comes out of the box. fscrypt and the like is not always installed, but it is simply obtained. Given that encryption passwords do not have to be user account passwords, even the root user might have issues unless they are aware of the correct passwords.

I really do not see how importing mails using the import export tools and moving as it suits you after they are imported would either require a text editor or lead to things being more disjointed. Perhaps I simply do not understand what disjointed means to you.

Thanks for taking the time to respond Matt, you are right about the security stuff. I still get shocked when, form time to time, I open a file in text and see readable information.

The problem I'm having with the disjointed folders is 1) I wasn't up to speed on things when I started hacking and 2) now there seem to be subprofiles in the profile folders. That wasn't me so it is either a product of the input/output tools or the profile manager or me hacking away with them (I didn't directly create the subprofiles).

Anyway I think I'm getting more familiar with things and may be on the path to fixing it with a little more time :)

Feeling the same pain -- merging over 350 Mailboxes from previous Employees into a single box due to server migrations and Linux/Unix desktop removals.. around 500GB needs to be pulled from individual (local) mailbox files into a single Team mailbox... is a-bit more ( cumbersome) since all documentation being tailored for the microsoft users and less on the unix users perspective. we only deal with the windows virus for extreme cases thus why all PST files over 512Mb must be converted to mbox format to be ingested. folder overlap is not a concern, but we use a root system with names of old employees to then allow the new offline datastore team owners the ability to root out the duplicates and manage the data before re-insterting it inot the mail system. will the simple single process work if I move all mailboXes to a simple top folder? example profile 1~350 perform the simple single system approach then create a folder called 1unique and put all contents into that folder and proceed to import the next profile in the same manner to a 2unique folder all the way to 350unique?

You can copy all 350 mbox files into the Mail/Local Folders location of the profile, and when TB is restarted, there will be 350 folders under Local Folders in the Folder Pane. Copy or move the messages from each folder into 1unique. As an alternative, there are also apps for merging mbox files.