There are 2 separate mailing lists, one on linux.org.mt and another on gmane.org. All posts to either are cross-posted to the other. However, the content on the main page of the linux.org.mt site is not related to either mailing list and needs to be created separately on the site.
linux.org.mt list
This is accessible via http://linux.org.mt/. To subscribe to a read-only feed, use the RSS feed from the 'Syndicate' area at the upper right side of the page.
To be able to post to the list, register on the site and log in if you haven't already done so. Click on 'Mailing Lists' on the upper left side of the page. The page will say 'Your current email address is currently subscribed to all lists' whether it is or not. Then click on the 'Mailman Interface' link and fill in the section 'Subscribing to MLUG-list' and press 'Subscribe'.
Posting can be done using a standard email client and the email address mlug-list@linux.org.mt.
gmane list
This can be read and posted to online at http://news.gmane.org/gmane.org.user-groups.linux.mlug. It can also be read in a news reader using the feed URL http://rss.gmane.org/messages/excerpts/gmane.org.user-groups.linux.mlug.
To be able to post messages directly from an email client, use an NNTP client. This is also the only way to post messages with attachments, as far as I can tell. Thunderbird has NNTP functionality built in. To set it up, select Edit, Account Settings in Thunderbird, then Add Account, Newsgroup account, and enter your name and email address, then put in the server name news.gmane.org and finish the dialog. Select the newly-created reader in the left pane of Thunderbird, and choose 'Manage newsgroup subscriptions' in the right pane. The navigate to gmane.org.user-groups.linux.mlug and check the box next to it. Note that you need the .org part of the path, otherwise you won't find the Malta user group.