SMTP problem

Yesterday, using Thunderbird, I created some new folders and moved messages into them including some older messages.
Today, in eM Client, I can see that these folders have appeared but only with messages that were received or sent yesterday. All earlier messages have not synched, probably due to their prior date.
Is this a known bug? Is there a workaround to get older messages to synch?
Thanks

One thing you can try is to right-click on the folder and choose Properties > Repair. If it is a Gmail or Gsuite account, right-click on the All Mail folder instead.