What was 'copies'?

You need to give us more information:

What was the name of the old folder and how many messages were in it?
When you copied the contents of the old folder into the new folder, did the new folder then contain the same number of messages?

Did you try IDW's method before attempting to copy the messages into a new folder?

Just so you know, a Pegasus Mail folder comprises two files. The name is the same for each, but the extension is different. The file filename.pmm  contains the mail data. The file filename.pmi is an index of the contents of the .pmm file. When you open a .pmm file, it reads the index and displays the subject of each message. Opening/viewing a message is achieved by referring to the .pmi and know where the message is in the .pmm

When you right-click a folder and choose Properties, the filename (.pmm) is displayed.

Finally, did you create a backup as instructed? 

Greetings,

This error message "Invalid Offset in index record" continues to return even after  reindexing of the F0L07EA1.PMM folder. I have looked through the folder and nothing is obvious as to the why.

Any suggestions for a permanent cure?

Thanks in advance.

[quote user="BMS"]Any suggestions for a permanent cure?[/quote]

Try reindexing after closing Pegasus Mail using <mbxmaint_ui.exe> which you'll find in Pegasus Mail's "Programs" subdirectory (defaults to <C:\PMail\Programs> if you didn't change it yourself).

And if that does not work create a backup, then create a new folder and copy the contents of the folder with the error into the new folder, then delete the old folder. Finally, rename the new folder so that has the same name as the one you deleted.

Greenman is spot on but be advised that you will need to reset any filters to the new folder regardless whether you end up with it named the same as the original one.

Thanks to all who have provided the feedback and solutions.

I created a new file and copied over all the data to the new file. Renamed the original to include (old) and the new file was named the same as the original.

This has solved the error msg issue, but I now only have have the several new emails in "copies". The new file does not display the 23k emails in my "copies" - have I erred in the process?