If this is an imap account then this is just a cache, and you can safely delete those files and Thunderbird will recreate them. Make sure it is not a pop account.

Who is the mail provider?

It's a pop account. The provider is Telstra of Australia.

How many messages are in the file? Have you tried compacting it?

Not sure about the number of messages.

Is there a way to compact the folder when it doesn't appear in the client?

Is it a defect as alluded to in this post? that mailboxes larger than 4 GB may be broken now:

https://thunderbird.topicbox.com/groups/developers/T4dccf32786db11d5-Mdc3f2ac68db21ac7cad3af03

If so, can I use an older client(pre-115) until this defect is fixed? Are the pre-115 clients available for download?

Yes, all prior releases are here: https://ftp.mozilla.org/pub/thunderbird/releases/ and specifically for final of 102 is here: https://ftp.mozilla.org/pub/thunderbird/releases/102.9.1/

I am unable to use the earlier versions as the profile which the Inbox is located in is from a later version.

I deleted the inbox.msf file and started Thunderbird hoping that the Inbox.msf file will be regenerated. However that didn't happen.

Any further suggestions will be appreciated.

Is the application,ThunderbirdRecovery, a safe product to use? I can't find any reviews of it.

http://www.emailadepts.com/ThunderbirdRecovery.htm

Please post a screen shot of your folder pane.

harshapereratrinco ?