Skip to main content

Securing Google Apps for Education GMail

Over the past year or so there have been lots of posts on various G+ communities about issues with GMail delivery (particularly to groups) and accounts being exploited by email spoofing. So I thought it might be an idea to bring together the steps you need to take to knock these issues on the head into one place.

The steps:

  1. Configure your domain to use SPF (sender policy framework)
  2. Configure your domain to use DKIM (Domiankey identified mail)
  3. Configure your domain to use DMARC (prevents email spoofing)
  4. Force all incoming SPAM into admin quarantine 
Numbers one and two will improve your email flow and prevent your messages (particularly ones going to groups and certain outside agencies) being marked as SPAM.

DMARC relies on the SPF and DKIM being correctly configured first. All messages you send will be checked and ones that fail either SPF or DKIM will be actioned in accordance with a rule you set.

The final step prevents end users ever seeing anything in their SPAM folder. All SPAM ends up in admin quarantine, thus preventing end users ever having the opportunity to click on nasty messages.

In detail

1. SPF
To enable SPF you will need to enter a TXT record in the DNS editor of your web hosting company. The record should be v=spf1 include:_spf.google.com ~all  
Your hosting company may have a specific section for email authentication where this record can be pasted in in the SPF section. Once enabled messages should have a 'mailed by' section in the details:
2. DKIM
To enable DKIM you need to turn on email authentication in the Google Apps admin console. So navigate to Apps, Mail, and look for email authentication.
There you have an option to turn on authentication (DKIM). There will be a TXT record name and value (a long key). In your domain hosting DNS editor create a TXT record. The name is the name shown in the Google Apps admin console - google._domainkey , the value is the long key - just copy and paste it. TTL I normally set as 14400.
Once you have saved the record in the DNS editor, make a cup of tea and read the paper. When you have finished, click 'start authenticating' in the Google Apps management console. If all is well it should go green. If not wait a little longer and just double check your work. To test, send a message to another gmail account. You should see:
3. DMARC
Now before you start on this bit be absolutely sure steps 1&2 are working. I'd give it a few days and check both SPF/DKIM work reliably. If all is well, continue. DMARC checks all messages you send from your domain and acts on any that fail either SPF or DKIM. 
To enable, create a TXT record with the name: _dmarc.your_domain.com
The valve should be: v=DMARC1; p=whatyouwanttohappen; rua=mailto:emailladdressformessages

So p can be: 
none - nothing happens if a message fails either SPF or DKIM
quarantine - messages that fail go into SPAM
reject - messages get rejected

You can also add the variable pct=X where X is the % of messages that the rule applies to. Not a bad idea to use early on just to see what gets stopped.

emailladdressformessages - the email address  that will get the daily messages that tell you what messages has passed and which have failed and why. I skip the inbox with these and filter them into a label called DMARC.

All being well, you won't notice anything much other than the daily messages. Assuming you have either quarantine or reject selected you will now be immune to email spoofing.

4. Force SPAM into Admin Quarantine. See my blog post here on how to do this.

As a footnote, I'd also say that you should never whitelist any domains or email addresses - ever. If all of the above of correctly configured, you should never have an issue with things being picked up as SPAM and therefore the need to whitelist domains vanishes. Whitelisting domains sort of says, please SPAM me - so don't be tempted to do it!





Labels:

Comments

Post a Comment

Popular posts from this blog

Delete a specific email using GAM

If a user send an inappropriate email to a loads of people or get stung by some sort of email exploit you can quickly delete the email from all of the recipients using a GAM command. Step 1 - get the email header Go into Google Vault and search for the offending user or someone known to have got the message. Click show details and grab the email ID. This will be a long string of characters followed by @mail.gmail.com Step 2 - find out who has the email Go into Google Vault and find the original message sent by the offending user. Look at the details to see who got it. Copy the list and dump it into a spreadsheet. Clean up to just a list of emails with a column header 'mail'. Save as a csv file. Step 3 - delete messages with GAM Put your CSV file in your GAM folder - this e.g. assumes its called mail.csv Run: gam csv mail.csv gam user ~mail delete messages query rfc822msgid: MESSAGEIDHERE doit The alternative nuke option is: gam all users delete messages query rf...
Post a Comment
Read more

Adding subdomains to G Suite

This is how I add subdomains (so basically new schools) to out G suite setup. I've got these steps documented on a scruffy set of notes that I've now got in Keep - so time to document them - for myself as much as anyone else! Steps in order (roughly) Add the new domain Verify the new domain Add MX records to hosting Add SPF record for Google to hosting Turn on email authentication Add DMARC record to hosting Setup custom Directory and restrict students OU to this. Create an admin quarantine for the domain. Configure SPAM setting for the domain. Turn on and off services as appropriate. Map a blank Google Site to the naked domain - if required. Setup some basic groups - allstaff, allusers (for directory) and students with appropriate permissions. Deploy custom wallpapers. So the steps in a bit of detail: Add the new domain & Verify ownership Click on Domains in the admin console: Add/remove domains followed by "add a domain" At this...
Post a Comment
Read more

My favorite GAM commands - well a few of them at least!

Where would be without GAM? Paying for expensive syncing tools or doing tedious manual tasks in the admin console. GAM can automate most things you might want to do in G Suite. So these are a few of my favourite commands - one I use either as part of a batch file - or just standalone. There are loads more - but these are ones that are used daily. Classroom Create a spreadsheet of all your domains classes -  gam print courses todrive Create a spreadsheet of a teacher's classes:  gam print courses teacher fred@mydomain.com todrive Bulk create classes: gam csv classes.csv gam create course alias ~alias name ~alias section ~subject teacher ~teacher status ACTIVE where classes.csv is a list of classes you want to make. Add teachers: gam csv teachers.csv gam course ~alias add teacher ~teacher Add students: gam csv students.csv gam course ~alias add teacher ~student Sync Students (in this example to a group - but could be an ou/csv file) gam csv grou...
Post a Comment
Read more