Guide to Canadian Deliverability and Throughput

At Postscript, the successful delivery of your messages is a top priority. We wanted to share a transparent look into the deliverability process. In this article, we:

  • Define deliverability and throughput rates - these two concepts together paint a better picture about how your SMS program is operating.
  • Discuss the current limitations of sending MMS to Canadian recipients.
  • Walk you through how to isolate Canadian-only subscribers in segments and subscriber filters.

To navigate quickly to specific sections of this article, you can select any of the hyperlinked sections listed on the In this article card.

Understanding Throughput and Deliverability

SMS Delivery measures outgoing SMS and MMS messages that are received at their intended destination. Deliverability measures the difference between total delivered messages and total outgoing messages.

Throughput Rate is the rate at which messages can be sent, or move through messaging "roadways", within a given timeframe. In other words, throughput rate measures how long it takes for a subscriber to receive your message. Throughput rate can vary based on how busy the messaging roadways are and what kind of phone number a shop is using to send messages (e.g. shortcodes vs. toll-free numbers). The type of phone number a shop uses to send messages determines the size of the messaging "roadways". Postscript sends your messages to the carriers quickly, however the throughput rate is controlled by carriers and limited by overall system constraints (including several other users, including non-marketing use cases).

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Sending messaging from a shortcode is like traveling in the express lane on a highway. It’s built for high volume and top speed (and has a higher cost) so these roads are accustomed to high throughput whereas sending SMS messages from a TFN is like traveling on a multi-lane highway. However, sending MMS from a TFN is like traveling on a congested 2-lane highway. When you send during peak sending times, the roadways are smaller and heavily trafficked. 

Postscript’s partnership with Twilio allows merchants three times the bandwidth we received for BFCM 2021. You can think of this partnership as opening up an HOV lane on a two-lane highway for SMS messages.That means better throughput for Postscript merchants on both toll-free numbers (TFNs) and short codes. While this partnership improves throughput rate, keep in mind that carriers have a finite infrastructure that is limited by overall system constraints (including several other users with both marketing and non-marketing use cases).

If you consider the holiday season, as many businesses prepare for their busiest time of year, the number of marketing messages increases. This additional volume can turn what is normally a simple drive down a big highway into a highly-trafficked drive as more cars get on the same highway. As a result, it takes longer to reach your destination.

Understanding Canadian Throughput and Deliverability

At this time, carrier restrictions limit Postscript's ability to send MMS messages to Canadian subscribers. The roadways MMS Canadian carriers employ are not built for A2P (application to person) mass MMS delivery. In fact, Canadian carriers only allow 15 MMS messages per minute, or 900 MMS messages every hour collectively system wide. 

This applies to all carriers and impacts all SMS marketing brands regardless of which platform you are using. To optimize the end-user experience and ensure that your messages are delivered to your subscribers quickly and effectively, Postscript delivers campaign and automation messages exclusively as SMS to subscribers located outside of the US. However, direct 1:1 messages to customers (e.g. response to a customer question) will have MMS capabilities to enable these rich conversations. 

We recognize that images, GIFS, and contact cards are important to brands that like to showcase their products to subscribers. The good news is our research shows that SMS messages are just as effective as MMS messages in terms of click-through rates and conversions. Looking at A/B tests between SMS and MMS message, we discovered the following:


Message Type Click-Through Rate (CTR) Conversion Rate
MMS 8.10% 1.06%
SMS 8.90% 1.07%

Postscript continues to work closely with Twilio and Canadian carriers to monitor opportunities for improvement of MMS roadway capacity. However, for now, any MMS message targeting Canadian subscribers will be converted to an SMS, meaning the media in the message will be omitted. If you’d like to craft Canadian-specific (sms-only) messages, we recommend taking advantage of Postscript's segmentation tools to isolate Canadian-only subscribers. We walk through how to use our segmentation tools in the next tabs.

Sending Messages to Canadian Subscribers

Campaign Segments Subscriber Filters in Automations

Canadian deliverability aside, hyper-segmentation is a best practice in the SMS marketing space. You will likely address your repeat purchasers differently than a brand new subscriber who has never purchased from your brand before. Segmentation allows your brand to create a more personalized and highly-tailored experience for your subscribers.

Postscript offers a variety of ways that your brand can segment subscribers. Below, we walk you through how to create a Canadian-Subscribers-Only segment (with additional criteria) so you can craft SMS campaigns targeting Canadian recipients only.


  1. Select Messaging on the left-side navigation panel within your Postscript Dashboard.
  2. Select Segments, then select Create Segment in the upper-right corner.
  3. Name your segment. Choose a name that will help you easily identify this segment when it comes time to build your campaign.
  4. Select your criteria by clicking the dark blue dropdown under Segment Criteria. To include Canadian-based subscribers only, select Subscriber Phone Two Letter Country Code.
  5. Select your logic by selecting equals and then selecting CA using the dropdown on the right right.
  6. Add criteria. Use the AND connectors to add criteria in addition to the CA-based criterion. Learn more about the AND/OR connectors here.
    • Tip: Additional criteria could be Number of Orders equals 0 to target Canadian subscribers who have not placed an order. Alternatively, you could use Number of Orders greater than 0 to target Canadian subscribers who have placed an order.
  7. Save. Once you’ve added your criteria, be sure to select Save in the lower-right corner.
  8. Add to your campaign. Once your segment is saved, you can add this segment to your campaigns or campaign flows to hyper-target your Canadian-based subscribers. Keep in mind, the idea here is to send multiple campaigns to a variety of target segments.
   NOTE: Exclude Canadian Subscribers in Flow Builder If you intend to send an MMS campaign and would like to exclude your Canadian subscribers to optimize throughput rate, you can do so by following the instructions above to build your Canadian-only segment, then adding that segment to the Excludes field of campaign properties.

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