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Sending Bulk SMS via Contacts

Looking to send personalized SMS messages to a large group of contacts quickly and efficiently? With the Bulk SMS feature in Stack's Contacts tab, you can compose, schedule, and track SMS campaigns at scale. Whether launching a promotion or sending reminders, this guide will walk you through the process—fast and effectively.

Table of Contents​

What is Bulk SMS​

Bulk SMS allows you to send a single SMS message to multiple contacts simultaneously. It's particularly useful for marketing campaigns, service reminders, or time-sensitive updates. This feature enables direct communication with your audience—all from the Contacts tab.

Key Benefits of Sending Bulk SMS​

Understanding the benefits of this feature can enhance your communication strategy. Here's why Bulk SMS is a game-changer for your business:

  • Save time by messaging multiple contacts in one action.
  • Ensure consistent communication across large audiences.
  • Personalize messages with custom fields or templates.
  • Flexible delivery options: Send messages instantly, schedule them, or use drip mode.
  • Track delivery results via the Bulk Actions dashboard.

How to Send Bulk SMS via Contacts​

Learn how to send SMS in bulk—from selecting contacts to scheduling messages and monitoring results.

Select Contacts​

  1. Use the checkboxes on the left side of the Contacts page to select the contacts you want to message.

Click the SMS Icon​

  1. Click the SMS icon in the top menu bar to open the Bulk SMS window.

Select the Sending Phone Number​

  1. Choose the number you want to send from in the "From Phone Number" dropdown. If left blank, the system uses the last number used per contact or the account default.

Compose Your Message or Use a Template​

  1. Type your custom message or click "SMS Templates" to insert a pre-saved message. Personalize messages using custom fields, and add emojis or attachments if desired.

Choose a Delivery Method​

  • Send All at Once: Instantly send your message to all selected contacts.
  • Send at Scheduled Time: Choose a date and time for sending the message.
  • Send in Drip Mode: Send messages in smaller batches.

For drip mode, specify:

  • Start on: Date to start sending SMS.
  • Batch Quantity: Number of contacts per batch.
  • Repeat After: Time interval between batches.
  • Send on: Specific days of the week for sending SMS.
  • Process between (hours): Specific hours for sending SMS, adjusted to the local timezone.
  • End At: Latest time of day for sending drip SMS. Messages outside this window pause and resume the next day.

Add an Action Description​

  1. Add a label in the "Action" field for clear reporting and tracking in bulk actions.

Click "Send SMS"​

  1. Submit your bulk message. Your action is now queued and will begin processing.

Track Progress in the Bulk Actions Tab​

  1. Visit the "Bulk Actions" tab to view the status of your SMS send, including metrics like sent, delivered, clicked, and failed. Click "Show Stats" for detailed results.

Frequently Asked Questions​

Q: What happens if I don’t choose a phone number in the ‘From’ field?
A: If no number is selected, the system defaults to the last number used per contact. If none exists, the account’s default number is used.

Q: Can I cancel a scheduled bulk SMS after it’s queued?
A: You cannot cancel a message that’s already sent, but you may be able to stop a scheduled or drip-based send by contacting support immediately after queuing.

Q: How does drip mode handle timezones?
A: Drip mode respects the local timezone of your account when processing time windows. All delays and send windows are calculated accordingly.

Q: Will unsubscribed contacts still receive the bulk SMS?
A: No, Stack automatically excludes unsubscribed or opted-out contacts from bulk sends to ensure compliance.

Q: Can I track which contacts failed to receive the SMS and why?
A: Yes. Go to the Bulk Actions tab > Show Stats. You’ll find detailed delivery reports including failure reasons like “invalid number” or “carrier block.”