Multi User E-mail Client

Is there an e-mail client software package that can support two concurrent users?

The situation is two users on a small network sharing a local e-mail filestore. Several e-mail addresses feed into the shared filestore and are then transferred from the Inbox to named folders, as appropriate, by either user. Long ago, Netscape Messenger did this by taking out a lock (Permission) when a folder was opened, to avoid it being updated by the other user at the same time.

Is there a modern client that has a similar 'locking' facility?

(Using Windows 10)

Not sure if Thunderbird will do it. Maybe look into it?

Hi wiganken,
Thanks for the suggestion. I've given it a try using Thunderbird v52.9.1. Unfortunately TB does not check if the other user already has a folder open when it opens it. Also it seems to keep folder indexes in RAM and doesn't update them until a change is made. This means that just viewing a folder will not see an update done by the other user e.g. a message moved in.

Latest TB is v78.8.1 (32-bit) so why did you install v52.9.1? That's very old.

I take it that you set your email accounts using IMAP (not POP)?

Hi wiganken,
The second machine, that isn't normally in use, that I tested the locking against is running XP, so Thunderbird v52.9.1 is the newest available. (It seemed unlikely that a locking facility would have been added in later versions of TB?)
The e-mail accounts were set up long ago in dial-up days, so POP3 was used. I think it would be very difficult to retrofit the folder structure to an IMAP server now.
Thanks for your help.

Wow! Still using Windows XP and POP.

Yes maybe you are limited there then. Sorry. Maybe someone e;lse can help. Good luck.