Guide to SMS and MMS Message Deliverability Issues

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   Sending to Canadian Subscribers? At this time, local carrier restrictions impact Postscript's ability to send MMS messages to Candian subscribers. You can learn more about MMS deliverability to Canadian subscribers here.

At Postscript, the successful delivery of your messages is a top priority. However, there are times when deliverability issues arise that are out of our control.

We wanted to share a transparent look into the deliverability process. We’ll take you through the process from start to finish and discuss which parts your shop, Postscript, and the carriers control. We’ll also discuss common causes of deliverability issues and recommend some best practices.

Postscript and Mobile Carriers


Postscript works with your shop and network carriers to deliver the messages that you create to your subscriber base. However, it’s important to break down which entity is responsible for which parts of the delivery process.

Your Shop Postscript Network Carriers

While Postscript and network carriers play an important role in the message delivery process, the below are the responsibilities of your shop to ensure you are viewed by the carriers as a trustworthy source.

  • Collect explicit opt-in consent from every subscriber using compliant list growth methods.
  • Create messages (including GIFs/images, copy, and promotional offers) to send to your subscribers.
  • Choose a phone number type (e.g., short code, toll-free, etc.) that best supports the volume of messages you wish to send.
  • Keep messages concise, engaging, and free of restricted content.
  • Provide opt-out opportunities (we recommend at least once a month).

What Impacts Message Deliverability


Several factors can impact message deliverability, and network carriers are responsible for the majority of these.

Carrier Peak Times Message Filtering Message Volume Phone Issues

Carriers experience peak activity time, whether it be a specific time of day, day of the week, or time of year. Increased activity and traffic create network congestion, which can delay a message or cause delivery failure.

This is especially common during holidays, in particular Black Friday and Cyber Monday. Many brands send campaigns to their entire customer base, which can lead to a large message volume that causes your message queue to overflow. Delays in sending are even more common for MMS campaigns since media files like images and GIFs use more data when sending.

What You Can Do

  • Send SMS campaigns. During peak time, carriers may experience difficulty sending MMS messages. It’s always a good idea to either send SMS campaigns during peak time or have a backup campaign message. This is especially important during BFCM so your message doesn’t get lost in the congestion. 
  • Send campaigns to smaller segments. Create campaigns tailored to different parts of your subscriber base using customer segments. Not only will this help with conversion, it can help keep your message queue manageable. The more targeted your messages, the better. At Postscript we believe in quality over quantity.
  • Target brand enthusiasts and repeat buyers. Rather than sending to your entire subscriber base, target subscribers who are regular purchasers as they are more likely to convert.
  • Enable SMS fallback for MMS campaigns during poor delivery windows. You have the option and ability to pause scheduled campaigns so that they don't send during times of poor deliverability. If you have a time-sensitive campaign, then it might be best to let it send as an SMS. Simply select the Pause MMS messages instead of SMS fallback checkbox on the Settings page accessible by clicking your shop name in the side menu.
  • Extend coupon deadline. Make more time-sensitive holiday sales span over longer periods so that coupons won’t expire (and customers won't miss out) should there be deliverability delays.

How Postscript Notifies You of Deliverability Issues


We will always keep you in the loop when deliverability issues occur. When our system detects a carrier issue with MMS message delivery, we'll notify you within the Postscript app.

We have two banners, both of which will display at the top of the page.

Issues Have Recently Occurred Issues Are Currently Occurring

Our gold banner indicates that our system recently detected issues with telephone carriers delivering MMS messages and we suspect those issues may occur again in the near future.

   Note: Issues with MMS deliverability do not affect SMS messages. This is because carriers use separate networks to deliver SMS (plain-text messages) and MMS (messages containing images and/or GIFs).

How Postscript Handles Deliverability Issues


As soon as our system recognizes that carriers are having issues delivering MMS messages, Postscript stops sending MMS messages.

Postscript also takes the following actions:

  • Temporarily prevents you from sending or scheduling new MMS campaigns. You can still send SMS campaigns by removing images or GIFs from the campaign.
  • Converts keyword replies and replies to MMS messages to SMS messages. Postscript will charge you the normal amount of credits for the SMS message but will not charge you over 3 credits per message. This ensures your message cost is less than or equal to the MMS message.
  • Converts current MMS automations and previously scheduled MMS campaigns to SMS messages. 

Get Support


Have questions? Please feel free to reach out to our wonderful Support team at support@postscript.io or via live chat. You can also submit a support request here!

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