Why does not the setting for Send back changed attachments take effect?

This setting can only be used if attachments were swapped out by the program.

This means in the original e-mail must exists an attachment called "AttachmentsManager.txt". In this file is saved the hash value of each swapped out attachment.

When replying or forwarding an e-mail the program gets the actual hash values from the attachments of the disk and compares it with the one saved in the file "AttachmentsManager.txt". Only if there is a difference the attachment will be added to the new e-mail..