At the moment, emails in the dormitory-based email account are accessible only by email clients like Thunderbird. We are working on the web client to be available again.
Web client is working again.
If you use a web client Squirrelmail and use diacritic when composing your mail, you need to have the environment language switched to your language for the client to encode your email correctly.
On the top of the screen, there is a link "Options". On the Options page, there is a link "Display Preferences", where you can set Language: Your language. You will need to refresh the page (click on the "Refresh Page" link) after saving the settings for the new language settings to apply.
Password to your dormitory-based email account is the same as the password to SINIS.
Settings for the email client can be found here.