SMS Relentless

License: GNU Affero General Public License v3

Version: 1.3.1
Release date: 2023-11-6

View in Nextcloud App Store
Git repository

SMS Relentlessβ„’ is a Nextcloud application that allows sending and receiving SMS and MMS messages in Nextcloud.

A,, or account and a real phone number acquired from one of the 4 providers are needed.


  • πŸš€ Use one or multiple local phone numbers in countries of your choice, to send and receive SMS/MMS messages with your browser, on any device connected to the Internet.
  • πŸ“‘ Sent and received SMS/MMS messages are stored in the database per sending/receiving user and can be viewed in paginated tables with filters for every column.
  • πŸ–ΌοΈ Up to 10 files of various formats, including jpeg, png and gif, can be sent as MMS messages from MMS enabled phone numbers. Files included in incoming MMS messages are not downloaded automatically. They are stored as URL links to the actual files, so that the receivers can download them only if they trust the senders.
  • πŸ“” SMS/MMS messages older than a specified number of days can be deleted in bulk with one click and they are automatically archived in csv files stored in Nextcloud, before being removed from the database. This makes them available for future analysis.
  • πŸ’» Sending SMS/MMS messages to thousands of recipients can be achieved by uploading a txt/csv file containing the recipients’ phone numbers and the same SMS/MMS is sent automatically to all. The time interval between two consecutive messages is configurable.

  • πŸ‘€ The Display Name of Nextcloud users can be prepended to their messages, to make the origin of messages clearer.

  • ⚠️ Admins can restrict the use of specific phone numbers to specific groups or users.

  • βœ‰οΈ Auto-replies in ‘daily mode’ and ‘vacation mode’ can be configured for any controlled phone number.

  • πŸ” SMS/MMS messages coming from Telnyx, Plivo and Twilio are checked for authenticity by verifying the SMS provider’s signature.
  • πŸ“§ Users receive notifications in Nextcloud and (optionally) emails when new SMS/MMS messages arrive.
  • πŸ“„ Each sent message receives a delivery receipt displayed in the Sent SMS Messages table.
  • πŸ“± It works with regular ‘long code’ (10-digit) phone numbers, but also with ‘toll-free’ numbers and ‘short codes’. Users see a list with their current phone numbers and can set them as Sender IDs. Setting alphanumeric Sender IDs is also possible.
  • πŸ’΅ It allows checking the current Telnyx/Plivo/Twilio balance by selecting the provider on the left panel.
  • πŸ’° The only ongoing cost is about $1 per month (depending on the country) for an SMS/MMS enabled phone number located in a country chosen by the user. No contracts.
  • πŸ’Έ Low prices per SMS: starting from $0.0060 per sent message and $0.0040 per received message (Telnyx), or $0.0070 per sent message and $0 per received message (Plivo), or $0.0099 per sent message and 0.0079 per received message (Twilio), or $0.0055 per sent message and 0.0040 per received message (Flowroute) in the USA.

Double Bastion is not affiliated with Telnyx, Plivo, Twilio or Flowroute.

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Send SMS message

Send MMS message

List received SMS messages

List sent SMS messages

Send SMS message to multiple recipients

Filter messages by date and keyword

Delete old SMS messages


SMS Relentless works with all major browsers.

Programming Languages

SMS Relentless only uses PHP, SQL, jQuery, CSS and HTML. This means it’s robust, efficient, light-weight and easy to maintain and debug.

Minimum Requirements

  • Nextcloud 22+ has to be installed and properly configured, preferably by following the Install Nextcloud chapter in our guide.
  • A,, or account and an SMS/MMS enabled phone number associated with it.
  • The libcurl PHP library has to be installed on the server (it’s usually installed automatically when PHP is installed).

To enable email notifications for every received SMS/MMS, the sendmail utility (/usr/sbin/sendmail on Debian Linux), has to be present on the server. sendmail is a binary which gets installed when Postfix is installed. Also, the web server user (www-data) has to be allowed to send emails from command line (by specifying authorized_submit_users = www-data in /etc/postfix/ for Postfix on Debian).


This chapter of our Complete Guide to a Complete Linux Server explains in detail how to install and use this application.

SMS Relentless is a component of RED Scarf Suite. It can be installed and used alone, but if you want to install all the components of RED Scarf Suite, you can follow our complete guide.


The GitHub SMS Relentless repository is just a pointer to the official SMS Relentless repository. We don’t use GitHub for developing SMS Relentless because GitHub is owned by one of the companies that proved their disrespect for digital freedom over the years and because centralized services create autonomy and privacy issues, in spite of all the benefits.

If you want to contribute code to this project, please submit this form, mentioning your intended changes. We’ll send you the credentials needed to push code to the “contrib” branch of the official repository. After we review the changes, we can include them in the project.

Please post any bugs that are not security related, or feature requests, on the issue tracker. If you notice bugs related to security, don’t post them on the issue tracker; instead, send them to manager [at] doublebastion [dot] com .


SMS Relentless as a whole is licensed under the GNU Affero General Public License Version 3. If you use SMS Relentless or distribute it in modified or unmodified form, you will need to comply with the terms of the GNU Affero General Public License Version 3.

SMS Relentless includes libraries licensed under different free software licenses. These libraries contain their respective original copyright notices.

If you have any questions, you can send them to: