Maybe this is a QMailServiceAction general problem, but I've checked it just with QMailRetrievalAction so far.

If we perform a "retrieveMessageList" query, when the activity has changed to "QMailServiceAction::Successful", it is not expectable that any other signal could arrive after processing the "activityChanged" signal. However, a "progressChanged" signal is arriving after the "activityChanged" one.

This could lead to some problems when we are performing several queries with the same QMailRetrievalAction instance. How we will know if the progressChanged signal has been triggered because of the previous or current query?

This is clearly a potential problem.

See the attached example which prints the signal arriving order.

Notice that I've not checked this with the "QMailServiceAction::Failed" activity but it could be that the same problem is happening. The same for the other QMailServiceAction subclasses.