A semi-common magic item that once existed in great kingdoms of the past was something known as a parcel. This could take a number of forms, but the most popular was that of a sturdy leather bag, covered in carved runes. There was a pocket on the outside of the bag, into which a personal or identifying item of some sort for a particular individual was placed. Thereafter, if a letter or very small package (such as gems in a tiny cloth bag, etc.) was placed within the large pouch of the parcel, it would magically appear in or around the person to whom the identifying item in the outside pocket is bound. Some of these could work across short distances, some across any distance, some across planes of existence, and some were rumored to even work across time itself.
Inevitably, when an item type becomes well known, those with nefarious plans will get involved. This particular parcel is cursed. It will appear to be one of the semi-common sort in all respects, and will radiate magic.
Once per day, this parcel may be used to send letters or small packages to a linked individual. It can work over any distance but not across other planes of existence (or through time). Tiny items sent via this parcel will arrive without issue, but written documents, like letters, lists, maps, or what have you, always arrive altered in some substantial way -- though not necessarily in an obvious one. Letters will be rewritten to add, omit, or completely make up false facts and fraudulent details. Maps will have fictitious landmarks added, or important ones removed. Lists might well lose a few items, etc. The parcel will twist whatever is sent so as to turn the communique into something negative for either the sender or receiver (or both).
This can be a treacherous item to rely upon, but does not require a Remove Curse for the owner to be rid of it; it can simply be discarded or destroyed.
Neutering museum in Komňa-bag by Jan Kamenicek under a Creative Commons Attribution-Share Alike 3.0 Unported License modified in Inkscape by David