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Below you will find a list of all our current hosts and their IP addresses. This could be usefull to setup your SPF record in case you also use our services for outbound e-mail scanning or to allow SMTP access to your mail server.







If you are sending outbound e-mail through our servers please do not forget to add ip4: to your SPF record!

– F.A.Q. –

How do I add a domain?

As soon as you have an account with us, you can easily add a domain. This can be done through our portal. Go to ‘Dashboard’ and click on the ‘Add Domain’ icon.


Choose the desired product (inbound only, outbound only or both). Fill in the domain name, the mail server’s IP-address and the number of mailboxes, and you can start (after adjusting the MX-records).

MX-Relay add domain

Can I use per user quarantine?

Yes you can. You can give every user a personal account and ‘inbox’ on our filters. As soon as an incoming email meets the quarantine score, it will be delivered to the inbox. The user receives a daily message with a handy overview and a link to the web interface of our filters. Here you can view the messages and still release it if required.

Login as domain admin and go to ‘Basic’, ‘Spam Checking’ and adjust the desired Quarantine score. This should be a score between your ‘Tag’ and ‘Block’ score.


Next go to ‘Basic’, ‘Quarantine’ and make sure the ‘Quarantine Type’ is set to ‘Per User’.


You have now finished and can use the Quarantine function.

Why should I send my outgoing mail through MX-Relay?

Many companies intently filter incoming mail, but forget about the risks of outgoing mail. More and more, infected mail servers or computers within your own network are sending out spam and/or malware without you knowing it and with what consequences?

You could be placed on a blacklist, preventing everybody from sending out emails. The administrators have to track down the infected computers to try to remove the unwanted software. You could be spending days trying to be removed from the blacklists. In short, it will cost you a lot of time and money.

Can I send my outgoing email using a different port (instead of the standard port 25)?

Yes you can! For many of our costumers the standard port for email (SMTP port 25) is blocked. As soon as you use our outgoing email service, you can send your email using the following ports:

25, 26, 27, 2525, 2500, 587

Should you wish to send your email using a different port, you can let us know via email.

Quick search in the message overview.

We have chosen to use most of our system’s capacity for processing email messages. Searching through messages can therefore be slow at times.

To speed up the search through all your messages we can give you the following tips:

Always set your browser language to ‘English’


Always use a ‘time’ filter before your start your search. You might set it to all emails from the last 3 days.


Email is being blocked for the reason of ‘zero hour intent’, what does that mean?

Messages being blocked for the reason: ‘Zero hour intent’ contain a part of a domain/URL where Barracuda has noticed malware coming from. When you have found the header information of the message, it will look like this:


It is pointless to put the domain concerned ‘’ on the whitelist, as the message could very well contain viruses which you really wouldn’t want on your network.

You can visit the following Barracuda website to check if the domain is still on the intent list: and to request it being released. Please type the domain under ‘lookup’:


In this example the domain ‘’ is still on the Barracuda Intent list. If this is the case you should contact for more information and a possible removal request.

It is often not your own (or costumer’s) domain, but a receiving third party that is on this list. It should really be the responsibility of this party to be removed from the list, because none of the Barracuda users around the world are receiving any of their emails.

I still receive spam in my mailbox from time to time, what should I do about this?

Should you still receive spam in your mailbox, you can take the following measures:

Search for the message in question in the message overview, tick it and go to ‘More Actions’, then click on ‘Submit to Barracuda Central as Spam’.

Mark as spam

If you can’t find the message in the message overview, chances are the email didn’t go through our filters, but was delivered directly to your mail server. Check if the message went through our filters by looking at the header of the message to see if it was sent through one of our machines (filter01, cluster02 etc.). Sometimes a mail server is still open on port 25 (SMTP) and spammers will be able to directly deliver mail to your mail server. It is best to only allow SMPT traffic from our hosts:

Where can I change the IP number of our mail server?

You can simply change the IP address or the FQDN under ‘Basic’, ‘IP Configuration’. You can fill in the IP address or the FQDN of your mail server under ‘Destination Server’.

Change the IP address

How do I remove a domain/stop invoicing?

After logging on to our portal, go to ‘Overview’. Next to your domains is the possibility to request outbound mail and also to remove the domain.

Beware! As soon as you click on ‘Delete’, invoicing will stop, but the domain will also directly be removed from our spam filters. Make sure your email is delivered to your mail server via a different route before you delete.


How do I request outbound email?

Outbound email can be requested in 2 ways. You might already have a domain for inbound email and decide you’d like to have outbound as well, or you have a completely new domain and wish to only have outbound.

You already have a domain for inbound and would like to have outbound as well
Log on to our portal, go to ‘Dashboard’ and klick on ‘Domains’.

MX-Relay domains

You will see an overview of domains:

My Domains

Click on ‘Request Outbound’ and outbound will be requested for your domain.

You have a new domain and wish to only have outbound.
Log on to our portal, go to ‘Dashboard’ and klick on ‘Add Domain’.


Choose ‘Outbound’ first and fill in your domain etc.

MX-Relay outbound

You will then receive an email from us to confirm your request and you can get started!

We send outgoing email through MX-Relay, can I see a message overview from these as well?

No, that is not possible. The outbound cluster is configured specifically to send a large number of messages. The spam core is a bit more loose here and there is no possibility for white- or blacklisting. The main reason to send your email through the dedicated outbound cluster is to minimize the chances of getting blacklisted and retain your company’s good reputation. When something does go wrong while sending a message, the cluster will bounce the message to the mail server in most cases so you can find out what exactly went wrong. Should you wish to rule out anything, you can always send us an email with the request for a specific search.

Why has an email not reached the mailbox?

This could have several reasons. First, do the following checks:
See if the MX-records of the domain in question are set correctly. This might be done through the website ‘MX Toolbox’. If all is correct, MX-records are only pointing to our spam filters. If there are any referrals  to other machines, some messages could have gone through that MX-record and not through our filters.
A second option is to search for the message in question in our filter. Go to ‘Basic’, ‘Message log’ and start your search. When you have found the message, take a look at the following:


Double click on the message for more information. The most important are ‘Action’, ‘Delivery Status’ and ‘Delivery Detail’.  Our filter is not blocking the message if Allowed is stated with ‘Action’, as is shown in this illustration. When the mail server does not accept the message it shows Rejected in ‘Delivery Status’. When this is the case you will often see more information in the ‘Delivery Detail’ such as a short error code. To help you on your way you could look up the complete ‘Delivery Detail’ information in google for example.

What is the maximum size allowed for an attachment?

At the recommendation of the manufacturer we allow a maximum size of 24MB.

Do you often send large files? We advise you to use a service such as for example.

Which attachments do we block?

We block the following attachments (these are also looked at in zip-files):

– Executables – Windows Executables
– Executables – Windows Scripts
– *.pif
– *.scr

Due to the large increase in crypto locker viruses we also block the following file types:

– *.docm
– *.dotm
– *.xlm
– *.xlsm
– *.xltm
– *.ppsm
– *.pptm
– *.sldm

The following attachment types are put in quarantine (regardless of whether or not you use quarantine boxes):

– *.ade, *.adp, *.bas, *.bat, *.chm, *.cmd, *.com, *.cpl, *.crt, *.dll, *.hlp, *.hta, *.inf, *.ins, *.isp, *.js, *.jse, *.lnk, *.mdb, *.mde, *.msc, *.msi, *.msp, *.mst, *.pcd, *.reg, *.sct, *.shb, *.shs, *.vb, *.vbe, *.wsc, *.wsf, *.wsh

Should you wish to add certain attachment types, please use the form below to send a request.

I have an inkling that not all messages are shown on the overview, how can this happen?

Check the following settings under ‘Basic’, ‘Message Log’:

view local messages

If the ‘Cluster Settings’ box under ‘Settings’ is ticked, you’ll only see the results of one unit from a cluster.
A cluster consists of several units, a load balancer decides which message will be processed through which unit.

Can I get an account on the filter to have a look at the configuration?

Yes you can. We can add users for you. This could be a user with ‘viewing’ rights only or a user that can also make changes to the configuration.
Notify us of which user you would like to add (this has to be an email address within the domain) and we will add it for you. Please use the form below.

Is this a completely Dutch service?

Yes, we are a Dutch company. All our servers are in datacentres in the Netherlands (namely: The Hague, Zoetermeer and Delft).

For how long do you store emails?

For the benefit of trouble shooting we use a log rotation of 9 days. Should a client’s mail server become unreachable, we will still try to deliver the messages for up to a maximum of 4 days ( 96 hours ).

If you can not find your answer in the F.A.Q. above, please do not hesitate to use the support request form below!