Mailrelay API Reference

SMS campaigns

SMS campaigns are the text messages that you send in bulk to your groups or to a list of phone numbers. Each campaign has a sender name, the message and, optionally, link tracking.

Since 15 September 2026, Spain's CNMC requires every alphanumeric sender name (alias) used towards Spanish numbers to be registered in its Alias Registry. Request the registration of your sender names in the SMS alias registry section of your account before using them.

Messages to Spanish numbers sent with an unregistered alphanumeric sender name are delivered with a random numeric sender instead. Numeric sender names and recipients outside Spain aren't affected.