Swedish to English Other General / Conversation / Greetings / Letters

The text I'm looking at now (about a file-transfer system) uses a lot of words with "-post", including but not limited to:

- sändningspost
- filpost
- inledningspost
- adresspost
- slutpost

These "post"s appear to consist of strings of symbols (e.g. a "sändningspost" could be something like %111).

Is there an English word that could translate "post" in all the above cases, or does it have to be rendered differently in each/most of the above terms?

Thanks