Remove “EXTERNAL” Tag from Exim Emails

-
In an earlier post I mentioned how to tag/add EXTERNAL to the subject header on exim.  I made the changes on our Sophos UTM which may require re-applying the configuration files after Sophos UTM update.

I ended up adding and elif block to act on outgoing emails in the exim.system_filter file

this is the block I added.  Change your domain as appropriate and add additional lines if you need to.

elif
 $header_from: contains "@yourdomain.com>"
 and $header_to: does not contain "@yourdomain.com>"
 and $header_subject: contains "[EXTERNAL]"
then
 headers add "Old-Subject: $h_subject:"
 headers remove "Subject"
 headers add "Subject: ${sg{$h_old-subject:}{[[]EXTERNAL[]]}{}}"
 headers remove "Old-Subject"
endif

This is the full exim.system_filter file

To have the $h_from or $header_from act on the domain part and not the display name part if someone was trying to spoof the from name I added the > at the end of the domain.  If you have alert domains that do not add display name they will get tagged with EXTERNAL.  You can add the full email address for those from addresses.

you will need to edit the exim.conf and add the line
system_filter = /etc/exim.system_filter
then restart exim

On Sophos UTM 9 to restart exim
/var/mdw/scripts/smtp restart

if
 $header_from: does not contain "@yourdomain.com>"
 and $header_from: does not contain "name@internaldomain.localdomain"
 and $header_from: does not contain "@anotherdomain.com"
 and $header_from: does not contain "@rt.tricongeophysics.com>"
 and $header_subject: does not contain "[EXTERNAL]"
then
 headers add "Old-Subject: $h_subject:"
 headers remove "Subject"
 headers add "Subject: [EXTERNAL] $h_old-subject"
 headers remove "Old-Subject"
elif
 $header_from: contains "@yourdomain.com>"
 and $header_to: does not contain "@yourdomain.com>"
 and $header_subject: contains "[EXTERNAL]"
then
 headers add "Old-Subject: $h_subject:"
 headers remove "Subject"
 headers add "Subject: ${sg{$h_old-subject:}{[[]EXTERNAL[]]}{}}"
 headers remove "Old-Subject"
endif


Sam Saqr
Location: Houston, TX, USA

Popular posts from this blog

Meal Prepping: The Key to Diet Ease and Compliance for Healthy Weight Management

-
Image
Figure 1: Batch once, eat well all week. Meal Prepping: The Key to Diet Ease and Compliance for Healthy Weight Management “You don’t have to eat less — you just have to eat well.” Meal prepping is the most practical way to eat healthy on busy schedules. By cooking in batches and portioning ahead, you eliminate decision fatigue, control calories without obsessing, and make it easier to hit protein and micronutrient goals. This 2025 guide gives you a step-by-step framework you can repeat weekly — plus a 7-day example plan, storage safety, and quick reheats. Quick Navigation Why Meal Prep Works The 90-Minute Meal-Prep Framework Food Storage & Reheating Safety 7-Day Example Menu (15-Minute Reheats) Macros Made Simple Budget & Time Savings FAQ Why Meal Prep Works Removes friction: Decisions and willpower happen once (on...
Read more

Balanced Bites: The Secret to Sustainable Weight Loss Through Macro and Micro Nutrients

-
Image
Figure 1: Balanced nutrition supports sustainable weight loss in 2025. Balanced Bites: The Secret to Sustainable Weight Loss Through Macro and Micro Nutrients “A healthy outside starts from the inside.” — Robert Urich Weight loss isn’t about cutting a single food group or following the latest diet trend — it’s about creating balance. Whether you’re trying Keto, Paleo, Whole30, or Mediterranean, understanding your macro and micro nutrients can transform how your body burns fat, builds energy, and maintains muscle. Let’s break down how to make that balance sustainable in 2025. What Are Macronutrients (and Why They Matter) Macronutrients — or “macros” — are the three main nutrients your body needs in large amounts: protein, carbohydrates, and fats . Getting the right ratio of these can make or break your fat loss and energy levels. Protein builds and repairs muscle, supports metabolism, and keeps you full. Lean meats, fish,...
Read more