Missing "Undo" functionality

Here are some examples of things that can’t be undone in eM Client:
-Creating a new calendar appointment, task or contact.
-Resizing a calendar appointment.
-Moving a calendar appointment to another date/time.
-Renaming a calendar appointment or task.
-Changing properties of a calendar appointment, task or contact.
-Moving a calendar appointment, task, contact or e-mail from one list/folder/account to another.
-Changing an e-mail’s “read” status or categories.
-Flagging an e-mail.
-More than one change in any text field.

Yes, that is true but most of them are actions which simply cannot be un-done at all.

I don’t agree. I think every single one of the items I described is reversible, at least to an extent that a user would expect. (I know that they aren’t all 100% reversible without side-effects, but from a user’s perspective, I don’t think it matters if other changes are made to cause the appearance of the original changes being reverted.)

Here are suggested reversions to do so:
Creating items: deleting items
Resizing appointments: changing the times back to the previous ones
Moving appointments to different dates/times: changing the times back to the previous ones
Renaming an item: renaming it back to the previous name
Changing item properties: changing them back to the previous ones
Moving items to different folders: moving them back
Marking an e-mail as read: marking it as unread
Marking an e-mail as unread: marking it as read
Flagging an e-mail: unflagging it
Unflagging an e-mail: flagging it

The the program is already able to do all of these reversions (done by the user). This is very important functionality.