New Spam Filtering

August 16th, 2016  |  Published in News

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 (


Spam filter upgrades and policies

January 24th, 2016  |  Published in News

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

April 10th, 2013  |  Published in Status

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.


Runbox listed by

October 10th, 2012  |  Published in Status

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

June 21st, 2012  |  Published in Status

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!


Fixed: Spam problems

February 15th, 2012  |  Published in Status

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.


Major spam filter upgrade

June 24th, 2010  |  Published in News

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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