You can save email message name(as an example, shown below) in the queue and then get that name from queue, fetch respective message/file from the folder and process it.
yes by adding emailName to the queue or by any adding any other related stuff you want to put on queues for same.
And answer to your another question regarding changes required without making use of queues, no they are not that much once you know what needs to be done.
I am attaching a sample template of re-framework which doesn’t use queues, you will see how its ‘get transaction data’ state is modified to retrieve data items from datatable instead. ReFrameWork-WithoutQueues-main.zip (971.0 KB)
I am also attaching youtube video link which demonstrates steps to modify your re-framework without using queues(its a small video):