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In spite of much searching on the internet, I can't really get an adequate understanding of this topic, perhaps because it combines multiple elements. As a result, I'm really worried about the state of my e-mail security.

The website/mail server is hosted on a shared Apache server. E-mail is POP3 and secured only by password. I access my e-mails through Thunderbird, which first time round warned me that I have an insecure mail server and that e-mails sent are wide open to prying eyes etc.

The question is: Can I do anything or should I avoid using that e-mail address?

How does encryption (e.g. via Enigmail) work? Will it protect me in this set-up? Does it only work if the recipient also has encryption software?

It strikes me that there are perhaps two different but related concerns: 1. Security of the shared hosting mail server. 2. Security of e-mails sent via the mail server. While I should surely be concerned about number 1, my main priority right now is number 2.

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2 Answers

There appears to be two security issues in your post. The first is the security of your connection to the web server i.e. the security of your password/credentials. The second is the security of messages you send.

I suspect the warning you saw from thunderbird was about your credential security. If your POP and/or SMTP server require passwords and they are not using SSL/TLS, then those passwords are being sent to the server in clear text and could potentially be intercepted by someone else, giving them your password. If your service provider is unable to provide encrypted channels, I would change service provider. There are plenty out there which do. If you must use that provider, I would make sure that the password you use is unique to that service and not one you also use for other services.

The second issue concerning the security of the messages you send - bottom line, email is inherently insecure. You can encrypt your messages, but then people you send mail to must have the software to decrypt it and must have your decryption key (i.e. public key). Encryption of mail messages is supported by many mail clients these days and much easier than it use to be, but it requires additional effort for both the sender and recipient. You need to manage private and public keys and your recipients must be prepared to and able to retrieve your public keys and have a setup configured to use them.

There are no absolutes here. You need to consider both the risks and convenience aspects of email. What is the value of your messages to others and how difficult do you need to make it for unauthorised people to see your message so that the cost of doing so exceeds the value such action would bring. Encrypting your birthday greeting to your grandmother is probably overkill. There is unlikely to be any real value for anyone else and the inconvenience to her will likely be greater than the value of your message (not to imply she doesn't value your birthday wishes of course!). On the other hand, the email you sent to your accountant containing all your banking details has a lot more potential value to an unauthorised reader, so encryption would probably make more sense. Likewise, your accountat is also more likely to have support for accessing encrypted messages if this is their preferred means of communication (though I would personally still prefer a more secure channel for providing such information).

Tim

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Assuming the server supports SSL/TLS (i.e. it has a valid certificate), it is possible to protect the email communications between the server and the user with SSL/TLS. This is especially important for the password - without this the password will be sent in the clear. But that won't protect the email communication between your server and other servers (assuming you send emails to other people that don't use the same server you use) or between the other servers and their users. For more details see Can I expect my e-mail to be routed securely?.

For this you need some form of email encryption. For email encryption to work both the sender and the receivers of the email must use compatible email encryption software and must share public keys. I believe Enigmail is OpenPGP compatible and should be compatible with any other OpenPGP compatible software.

As you note another concern is the security of the emails at rest - i.e. on the server. This is a greater risk in that an attacker who breaches the server will have access to all emails that are on the server including historical emails. An attacker who can read the communications between a user and the server can only read current emails. For the same reason it is most critical to protect the password than to protect the emails in transit - an attacker with the password can read all of your emails, including your future emails. Details on how to protect an Apache server can be found here.

For a great analysis and recommendations on how to secure emails, please see the NIST Guidelines on Electronic Mail Security.

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