Can ISP block selected e-mails?

Discussion in 'Computers' started by Cammacci, Oct 21, 2009.

  1. Cammacci
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    Cammacci Rookie

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    Hi.

    I'm not interested in legal aspect, just technical. I know it's not right. But there are still governments which practice censorship.

    I'm not asking about spam filters. Those can be applied by mail service providers, which is different from ISP. Say my mail SP is Yahoo Mail, my ISP is Comcast for example. Comcast is not controlling Yahoo severs. But can control traffic from Yahoo server to me. Right?

    The situation: ISP blocked a website. Now most likely it will try to filter subscribed distribution mail from this site.

    Can an ISP filter my emails using information in the headers? The e-mail which I access through browser (not an e-mail client)

    If yes, Can this be avoided?

    Apparently I'll see the subject line, but will I'll be able to receive the body of the mail? The text? What if there is no text just attachment, say zip file?
     
  2. DiveCon
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    no, they could block the website, but not the email content
     
  3. Cammacci
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    Cammacci Rookie

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    Correct me if I'm wrong. For example yahoo doesn't encrypt traffic during sessions so any information which is passing through ISP can be processed and filtered. And even if there are no key words in the body of the message, there is lots on information in the header including senders IP.
     
  4. DiveCon
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    ISP's dont have the capacity to filter at that level
    you are being paranoid
     
  5. Cammacci
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    I know examples. China, Uzbekistan and Iran. Recent reports were from Urumchi, China after clashes.

    They do it some how? How?
     
    Last edited: Oct 21, 2009
  6. Luissa
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    Luissa Annoying Customer Supporting Member

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    where did you get your name from?
     
  7. DiveCon
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    they block the entire site
     
  8. KittenKoder
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    KittenKoder Senior Member

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    Sites can block ISPs, ISPs can block sites or IPs, email is a bit different though ... it's complicated but let me see if I can explain it:

    Email messages have two types of content, remote and local. Local content (such as text) is loaded directly to the server and stored there, that can be filtered only by the email host (if you block it you can't see the email at all). Remote content however is not actually on the email server (most images and multimedia files in your messages are remotely hosted and embedded in the email). These can be filtered by email server or blocked by your ISP or even blocked or filtered by you. Countries which control their ISPs (like China) filter the actual email servers, block sites, etc. before they get to you.

    It would be possible for any ISP to choose to block any website they choose, but if your email server is not blocked the only things effected would be embedded content.
     
  9. DiveCon
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    which is why the efforts by China are not that successful
     
  10. KittenKoder
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    KittenKoder Senior Member

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    Which is why China keeps trying to sue email hosts. :lol:
     

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