How do country's block politically charged spam? [closed]

Question

I have a friend who is returning to China shortly, and I wanted to stay in touch with him so I got his email address. I was wondering what precautions does China (or any other dictatorial regimes for that matter) have so that I don't send him or anyone else politically charged content? As far as I know, most of the spam filtering that takes place is based on text analysis and ip reputation. Is this the only methods used or are there more advanced features as well? I would think that if the email is carefully crafted in content and comes from an IP with a good reputation these methods could be evaded. Most of the information on the web I can find seems to talk mostly about blocking websites, not email.

Answer 1

They may use machine learning and data analysis techniques similar to those used for spam filtering to find seditious content. As with spam filters, if you chose your wording carefully, most likely it will get through (but you need to be aware of what wording they are filtering on so it might take some trial and error).

If you want to employ methods of communication which require you to send sensitive information you could opt using SMIME or PGP to encrypt your email's content (providing they let this true).