[AstralStorm]

There are a few exceptions, nevertheless, the postage itself is kept unopened. They're usually detected by specialized test equipment with very low false positive rates.

1) Explosives and biological agents. Likely detected by sniffers.

2) Radiological materials.

3) Heavy packages or letters may be opened and inspected, especially for customs purposes. Depends on the postal service.

4) Potentially xray may be applied.

None of this is really an obstacle to communication. By the way, phone service is not censored or modified in most countries either. Including cellphones.

[zAy0LfpBZLC8mAC]

(1) and (2) do not really apply to letters (i.e., communication), (3) only applies when crossing borders, and then it's not the postal/delivery service that is opening the package, but customs, and (4) at least over here would be illegal, too, if it can be used to read the mail. Both opening/reading the mail that you are supposed to deliver as well as listening to phone calls going through your network is a criminal offence.