Spam filtering

Using junk mail filtering to control spam

Junk mail filtering attempts to give you control of how you manage spam that arrives to your email account on the mail server. You can prevent mail flagged as junk from ever reaching your inbox, or alternatively filter it into a junk mail folder (the default). To configure your junk email filters you need to login to the mailbox manager web service. You can access the mailbox manager web interface at http://mailboxes.mtheory.co.uk or securely at https://mailboxes.mtheory.co.uk.

Note if you login securely you will get a warning that “the identity of this website has not been verified,” or “server’s certificate does not match the URL,” or “server’s certificate is not trusted,” in your web browser. This is because the mailbox configuration service is hosted by our ISP, Dreamhost, and the certificate is issued by them rather than us. Your browser will normally let you view the certificate. If you click on this your browser will give you the option to always trust this certificate or install this certificate. Either of these should resolve this problem for you.

Once you login you will see a screen similar to that shown below. You can configure quite a lot of things from the mailbox manager interface. Many of these features are pretty self-explanatory but more details can be found in this post.

Mailboxes main page

Under the heading Junkmail Quarantine there is the option to Configure Junkmail Settings? highlighted in red in the above image. Click through on this link and you’ll be presented with the screen below.

Junkmail settings options

Under the heading Quarantine Settings there are several options which can be configured:

  • Quarantine to IMAP folder? – If you specify a folder name here mail deemed as junk by the filter will be moved to this folder on the IMAP server. In the example above mail will be moved to the Junk folder. If you leave it blank mail will be quarantined and you will have to login to the mailboxes interface to view quarantined messages.
  • At what spam score should emails be tagged as spam? – You can enter a number between 1 and 999. The filter attempts to asses the likely hood of an email being spam. It does this by looking at the message headings, content of the email etc and giving the email a score. It then compares this score with your threshold and if it is above the threshold level it moves the email to the folder specified in the field above. In the above example the threshold level is set to 999 which means emails will never be moved. As a result the filter will do nothing. The lower the number the more aggressive the spam filtering. If you want to stop spam from getting into your inbox you will probably need to set the level between 1 and 10. It might be worth starting at 10 and reducing it until no spam makes it into your inbox. This will almost certainly result in mail your want getting marked as spam, you can fix this by adding these email addresses to your whitelist (described below). Alternatively if you only receive spam from a couple of email address you could set the threshold relatively high (perhaps 50) and then blacklist (described below) the address which spam you.
  • At what spam score should emails be quarantined? This is the same as the above except if you left the Quarantine to IMAP folder blank then the emails get quarantined on the server and never make it into your email box. The thresholds and whitelists/blacklists are the same as above. In this case the junk mail filter will send you one email telling you that messages have been quarantined with details of the messages. This can be configured in the next setting.
  • When should you receive quarantine email reports? If you left the Quarantine to IMAP folder blank and set the threshold to something low (like 4 as above) then email which the server thinks is spam will be held in quarantine. As already mentioned there’s a chance that the filter may catch emails you want to receive. Thus the system gives you the option to receive a single email with details of all the messages that have been quarantined. This email can be sent on a daily basis, on weekdays only, once a month or never as selected by the buttons. In the example above it is set for weekdays but as the Quarantine to IMAP folder is not blank the mail will be tagged as spam and moved to a folder on the IMAP server and no quarantine report will be sent.
  • Update settings – when you change any settings you need to click on the update setting button to save your new settings.

Under the heading Add Whitelist/Blacklist you can add email addresses and domains to your whitelist/blacklist. A whitelist is a list of email address or domains which you do not want the filter to move if it thinks they are spam. For instance if you got regular emails from some sort of online store (lets call it ‘Store.com‘) they may be from an email address something like no-reply@store.com. The filter may identify these as spam so if you want to receive these emails you could add no-reply@store.com to your whitelist.

Similarly a blacklist does the exact opposite and tells the spam filter that email from this address or domain is spam and should be filtered even if it doesn’t think it is spam.

You can add email addresses to the whitelist and black list by adding the address to the box under Email Address. You then need to chose whether it gets whitelisted or blacklisted from the drop down menu, set the priority and then click the Add button. For individual addresses set the priority to highest. For domains you may well want to consider setting the priority lower to high, low or lowest. This essentially subtracts a fixed value from the spam score for the email thus possibly keeping the email below your spam threshold. For instance you may get very little spam from email addresses with the domain @gmail.com. Thus you might want to whitelist this domain but you may still get the odd spam email so perhaps you don’t want everything to automatically get through, in which case you might set the priority to low.

Unfortunately there isn’t a set of universal rules which will work for everyone so you will just have to adjust the filter settings until you get to some sort of level were you are happy. For instance you might whitelist everyone in your address book and then set your threshold to be very low to catch everything else.

The screenshot below shows the addition of some email address and domains to the whitelist and blacklist. You can remove email addresses or domains from the whitelist/blacklist by checking the box next to the email address under the Remove Whitelist/Blacklist heading and clicking on the button Remove Selected.

Junk filter settings showing whitelist/blacklist

Finally if you have chosen to have mail quarantined you will probably want to access this email at some point. This can be done by clicking on the Quarantined Messages link next to the letter icon at the very top of the page. You will be presented with a screen as shown below but probably with some messages listed in it.

Quarantined messages

From this screen you can take one of four actions to deal with messages. You can select messages with the tick boxes and then click on one of the five buttons at the top of the page.

  • Move to Inbox – simply moves the message into your inbox so you can read it in your email.
  • Whitelist/Inbox – adds the email address to your whitelist so that email from this address doesn’t get quarantined again and moves the message into your inbox so you can read it.
  • Blacklist/Delete – adds the email address to your blacklist so that email from this address always gets quarantined and then deletes the message.
  • Delete – simply deletes the message from your quarantine.
  • Refresh – refreshes the list of messages in your quarantine.

If you don’t do anything with the messages in your quarantine they will get deleted after 35 days.

That is all there is to know about spam filtering on mtheory. Should you have any more questions then please get in touch with the administrator.

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