Can ISP block selected e-mails?

[Nader]

Hi. I think i'm this is the right place to ask this question.

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?

 

[Lexluethar]

If the email is going to be blocked, it won't even get to you and you won't see any trace of the email. The sender will get an error message saying they couldn't send the following addresses.

If the emails go through their servers they can censor / block an email by the sender, subject or body of the email depending on how they have it setup.

And most likely it won't filter anything, it will just reject the email alltogether.

 

[Nader]

What if my mail on a free mail service. ISP is not controlling processing on mail server. As an example I mentioned yahoo. When I log into my yahoo account I'll still see list of e-mails. Right? ISP can not block yahoo website? It's a big issue, but they can filter selected e-mails.

the scheme

Outgoing mail server ------>Yahoo mail server--------->ISP-------------->mail recipient

ISP just provides access to the internet, and not manages mail on yahoo severs.

The question - will I'll be able to get the text after I click on the e-mail subject on the list? If not, how ISP will filter it? Yahoo is not supporting encryption during session, just during logging. What if there is no text in the body of the e-mail? What if there only attachment? Can ISP filter such e-mail knowing properties of the file attached?

 

[wafflehammer]

well if you're using yahoo it's been quite ****ty lately...i get failure to send notices days and sometimes weeks after i send emails lately :|

 

[Nader]

The reason I'm asking I had experience. In Uzbekistan I tried to open some of my messages but I was getting message from the ISP about an error. Those were plain text, but contained censored words like "Andijan" "massacre" "government". I could access the site, could log in and see the list of e-mails, but couldn't open some. While others were perfectly accessible. That was web-based service - yahoo mail.

And there's only one state controlled ISP just it has many sub-providers with different names. I think they use Chinese channel.

In China users of other then yahoo email services complained about the same problem durin recent clashes in Urumchi.

 

[Nader]

What if there was no text in the body of the message? just an attached file, say zip or PDF, would it be possible to access it? Can provider block it?

 

[patonb]

Whosd computer were you using?? If it wasn't your own, then could be a simple filter..

 

[Nader]

Whosd computer were you using?? If it wasn't your own, then could be a simple filter..

No it was my laptop

 

[wafflehammer]

by the sounds of it, it might be a ISP blocking it :\

 

[Nader]

So if I'll use web-based e-mail and if there was no text in the body of the message? just an attached file, say zip or PDF, would it be possible to access it? Can provider still block it?