Adding new Senders to your Messaging Service may or may not affect your current Sticky Sender mappings. Below we detail different scenarios using the UK as an example destination (this example does not necessarily reflect current regulatory restrictions in the UK):

Example Scenario 1

• Sending messages to UK end users
• Current Messaging Service contains international phone numbers
• Add a UK phone number or Short Code to the Messaging Service

Existing sticky sender mappings to a UK recipient will no longer be used from:

• International phone numbers. The UK phone number or Short Code (short code taking preference over the UK phone number) will be selected for subsequent messages.

Existing sticky sender mappings to a UK recipient will continue to be used from:

• UK phone numbers
• Alphanumeric Sender ID
• Short Code

Example Scenario 2

• Sending messages to UK end users
• Current Messaging Service contains only non-UK numbers or Senders
• Add an Alphanumeric Sender ID to a Sender Pool

There will be no effect on Sticky Sender mappings on any Sender Type. Existing Sticky Sender mappings will continue to be used unless there is a regulatory change.

Responding to Regulatory Changes

Updating your Sender Type in a Messaging Service

Countries may update or change their regulations on what kinds of Sender types can be used to send messages to that country. This often requires customers to start using different Sender types to send messages to that country. These new sender types may need to be added to Messaging Services in order for messages to be compliant, to guarantee delivery and prevent errors. 

Messaging Services will always check existing Sticky Sender mappings between non-local sender pairs to see if they are compliant before sending a message. If the pair is noncompliant then the mapping will be broken and Messaging Services will reassign a different sender from the number pool based on current Sender Selection logic. If there are no compliant senders in the Sender Pool (eg. only international long codes) then the Messaging Service will select the best available sender (eg. an international long code if those are the only senders available) based on current logic and the message may be blocked later by downstream services. 

Customers should ensure that compliant senders are added to Messaging Services when compliance regulations are changed. See the SMS Guidelines for regulations in different destinations.

MPS considerations when moving from phone numbers to Alphanumeric Sender ID

You may be using multiple phone numbers in a single Messaging Service in order to increase MPS. If regulatory changes require you to start using an Alphanumeric Sender ID then your strategy to increase MPS will need change.

Alphanumeric Sender ID has a 10 MPS by default. If you require an increase to your MPS, please see this guidance: https://support.twilio.com/hc/en-us/articles/360057082693-Can-I-increase-message-throughput-MPS-for-an-Alphanumeric-Sender-ID-

Breaking Sticky Sender Mappings Manually

Option 1: Break mappings for ALL existing international phone numbers to the SPECIFIC destination by temporarily adding a phone number local to the destination:

1. Purchase a phone number local to the destination, eg. a UK phone number
2. Add the local phone number to the Messaging Service
3. All Sticky Sender mappings on existing international phone numbers will be broken for UK end users
4. Remove the local phone number from the Messaging Service

Option 2: Break mappings for SPECIFIC senders to ALL destinations by removing and re-adding those senders

1. Remove a specific sender from the Messaging Service
2. Re-add the sender to the Messaging Service
3. The Sticky Sender mapping will broken for ALL destinations from that Sender