Spam filter training via IMAP

You can now train your Runbox spam filter using IMAP. Simply use your email program/app to move messages to your Spam folder to report them as spam, and move them from Spam to any other folder to report them as not spam.

IMAP training works for both the Dspam and the Cloudmark filters, the latter of which is in an open beta test. To join the beta test, just go to Manager > Filter and turn it on.

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New Web Servers Deployed

Yesterday we deployed our new web servers, which are powering the Runbox web app at There are a few changes and improvements that were deployed at the same time, and that we would like to tell you about.

New login screen

Among other things you may have noticed that the login procedure has changed. This is related to the roll-out of our new Account Security features, which include Two-Factor Authentication. We will post more about this soon, but the important thing to note is that the new login regime is more secure than before. This also completes our transition to a new, global authentication system which we have described previously.

If you have problems logging in

If you are experiencing problems logging in, please make sure that your browser has the latest version of the login screen. You can do this by pressing Ctrl + F5 on Windows and Cmd + R on macOS. If this doesn’t help, please try to clear your browser’s cache and restart it. If this doesn’t help or if you are unsure how to accomplish this, please contact Runbox Support.

There are a few other wrinkles on the new web servers that we are currently ironing out, and besides a more powerful and reliable webmail service we have also deployed a new spam filter.

New spam filter in beta

The new spam filter is powered by Cloudmark, which is one of the strongest authorities on spam analysis in the world. You can try out the new spam filter by going to Manager > Filter and selecting “Cloudmark (beta)” under “Detect junk mail”. If you are already using Dspam (the trainable spam filter) you can select “Both” to activate Cloudmark and Dspam.

The Cloudmark spam filter will automatically catch more spam by comparing spam signatures (fingerprints) with the central Cloudmark database. If you click “Not spam” or “Report spam” to correct spam filter behavior in the webmail, a report will be sent encrypted to the central Cloudmark service. Select “Train using reduced email details” to only send a message signature instead of the full message when reporting misclassified messages.

The Runbox Aero webmail theme

And if you haven’t already done so, we recommend that you try out the Runbox Aero webmail theme, which you can find in Webmail > Preferences. This theme has a more modern design and includes larger and more legible fonts.

More new features to come!

Finally, with the new web servers we have also established a streamlined deployment system that makes the path from development to production much more efficient. We won’t bore you with details, but we can say that you can expect more exciting features from Runbox going forward.

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New Spam Filtering

Recently we have been testing a new component to our spam filtering system. This component is powered by Cloudmark, one of the most popular and powerful spam filter systems available. We would now like to make Cloudmark available to more customers.

How Cloudmark works

Cloudmark is designed to detect known spam better and works as a central authority based on reporting by millions of Cloudmark users. It would help us improve our implementation of Cloudmark to have more Runbox users testing it.

Customers who are testing Cloudmark don’t need to do anything different in the way they use their email. However, we ask testers to report spam (or genuine mail) that is not classified correctly to a special Runbox email address.

No data is shared with a third party when using Cloudmark, as it’s running on Runbox’ own servers. Any reporting done by our customers is currently only going to Runbox itself. When we implement a reporting facility back to Cloudmark in the future it will be implemented as a clearly marked option.

How to start using Cloudmark

If you are interested in having Cloudmark added to your account, or wish to ask questions about it, please let us know at Runbox Support (

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Spam filter upgrades and policies

New Spam Filter Servers

As part of our ongoing fight against spam, Runbox has recently deployed a new cluster of spam filter servers and made a few changes to how we deal with spam.

We now block a lot more spam by rejecting connections from servers that are known to send spam. Most of these connections are from virus infected computers, and it is relatively easy to identify these machines via their IP addresses.

Another change we’ve made is to upgrade SpamAssassin so that it performs more extensive checks of incoming mail.

This is the first among several steps we are taking to clear your Inbox of spam, and we will post more news about this in the near future.

Changes to Bulk Mailing Policy

We’ve also decided to tighten our policies on bulk mailing using Runbox’ outgoing email servers to prevent Runbox from ending up on blacklists used by other email services.

As email use continues to grow and more people around the world are online, so does the amount of email sent for marketing and promotional reasons. Often mailing lists are badly managed and people receive email they no longer want, so they mark them as spam instead of unsubscribing from them.

Meanwhile spam systems are getting smarter, and email providers create statistics from the actions of their customers. If a customer marks a message as spam (whether it is spam or not), this is recorded in a database, and it can result in those domains and server IP addresses being blocked.

Only a very small number of Runbox customers use our services for marketing and promotional messages, but this can still have an adverse affect on all Runbox customers. Therefore we have decided that Runbox can no longer be used for bulk mailing, and we are now changing our Terms of Service to reflect this.

If you are using, or are planning to use, Runbox for bulk mailings, please see our page about Bulk Mailing and contact Runbox Support.

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Countering the recent spam surge

Over the past 8-10 days we have seen a significant surge in incoming spam, especially about weight loss.

We are working to reject more of this type of spam centrally, and hope to have achieved this as of today.

But if your account is still severely affected, there are things you can do to improve the situation meanwhile:

Most of our customers report that their spam filter does catch the spam, but that going through the Spam folder looking for legitimate messages becomes too big a task due to the large number of spam messages.

If this is affecting you, please see the following article on how to set up an extra filter to separate the very obvious spam from the messages the spam filter is less certain about and that you should review manually:

If your spam filter doesn’t catch this type of spam, please make sure that your Trainable Spam Filter is enabled in Manager:Filter, and that you train any missed spam mails using the Report Spam button.

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Runbox listed by

Some users may have had mails bounce recently  with an error referring to a blacklist called, or no clear error at all. This is caused by the sole blacklist runbox’ mailserver IP address is on, which is a list which only blacklists mail servers for handling mail bounces in certain ways. Many other mail servers does it in the same way we do, but our large volume and problems with the IMAP bandwidth quota (now solved) have probably caused us to be on this list on and off for years.

This is NOT a spammer blacklist in other words, and it is irresponsible and uninformed to bounce mails based on any single IP blacklist, but especially this one. And recently, it seems that far more services use this list in such a manner. If your mails have bounced from a domain where you have contacts, we recommend sending them the following link:

We may become delisted as of Oct 12, and will update this post then if so.

UPDATE: We are currently delisted, but will update this post if we are re-listed.

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Spam filter improvements

We’re currently tweaking the Runbox spam filter configuration to catch more spam.

Specifically, we’ve fixed an error that caused messages with a valid DKIM (DomainKeys Identified Mail) header to pass straight through the spam filter. Since some spam unfortunately includes such a header we now scan messages regardless of their DKIM status.

We have also tweaked the spam score given to messages sent from dynamic IP addresses, which can also be an indication of spam (although most such messages are of course innocent).

We would be interested in your feedback regarding the spam situation in your own account and whether you see any improvements.

Thank you!

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Fixed: Spam problems

You might have noticed an increased influx of spam recently, and it’s caused by problems with the RBL (Real-time Blackhole List) we have been using at Runbox. An RBL is a list of domain names associated with spamming, and is used when filtering spam.

We’re working on a solution which will be better than what we had before, and hope to have it running within a couple of days.

Update: This was fixed on friday 17th of february when we implemented SpamHaus RBL.

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Major spam filter upgrade

We have performed a major upgrade of the main Runbox spam filter (SpamAssassin) to the most recent version (3.3.1) and it’s running a fresh spam rule set that’s more aggressive towards spam.

We recommend that you check your spam folders for any misclassified messages during the next few days, and correct your trainable spam filter (if activated on the Filter page) using the “Not spam” link if necessary.

Furthermore, we have implemented a global filter that rejects messages that are virtually guaranteed to be spam (i.e. if the SpamAssassin score is 7 or more). This will significantly decrease the amount of spam that passes through to the user-level spam filters, and decrease the load on practically all levels of the system.

No email will be lost as a consequence of this change — in the very unlikely eventuality that a legitimate message is rejected, the sending server will be notified that the message was believed to be spam so that the sender can try again.

For more information about how Runbox fights spam, see our Anti-spam section.

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