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Duplicate message protection

A duplicate message is the second and every further message with the same text sent to the same number. It rarely happens on purpose — more often it comes from repeating an API call after a timeout, from a double click on a button, or from one number ending up in the recipient list several times. BulkGate protects you against it, but the transactional and promotional routes handle it differently.

How the two protections differ

	Transactional message	Promotional message
What it watches	the same message repeated over time	duplicate recipients within one list
Reach	across requests, a 5-minute window	only within a single request
Default state	off	off
What you will see	the message fails with `duplicity_message`	the recipient quietly drops off the list

Transactional messages: the same message repeated over time

You turn it on with the duplicates_check parameter in the transactional or simple transactional API. It accepts on and off (it also understands true/false, 1/0, yes/no), and the default is off.

When it is on, BulkGate remembers this combination for every message sent:

Part of the fingerprint	Note
Account	applies across every application (`application_id`) under one wallet
Channel	the same text over SMS and over Viber are two different messages
Phone number	in international format
Message text	must match character by character — a different name, time or code makes it a different message

If a message with the same fingerprint arrives within five minutes, BulkGate discards it and it never reaches the operator.

Important

The five-minute window starts with the first message and discarded attempts do not extend it. Once it expires, the same message goes through again.

For a cascade message, the fingerprint uses the main cascade text, not the texts of the individual channels.

What you will see in the response

A single message — the API returns a duplicity_message error with code 400. See the list of error types.
A bulk transactional message — the discarded message gets the duplicity_message status and counts towards total.status.duplicity_message. The rest of the batch is sent as usual.

Caution

Think twice before using the protection for one-time passwords. If the code changes with every attempt, it never applies. If you send a fixed text, you will discard the second send within five minutes — and the user who pressed “Resend” gets no message at all.

Promotional messages: duplicate recipients within one batch

On the promotional route nothing is remembered between requests. BulkGate simply goes through the recipient list built from a single request before sending and keeps the first occurrence. The duplicates_check parameter in the promotional or simple promotional API has three values:

Value	What it removes
`same_text`	the same message repeated to the same number
`same_number`	any further message to the same number, even with a different text
not set	nothing — the list is sent exactly as you submitted it

Note

The removal is silent — the response carries no status and no duplicate counter. The only trace is a lower recipient count than the number you submitted. If nobody is left after the removal, the request fails with no_recipients.

Two consecutive requests do not see each other. Send the same recipient in two batches and both messages go out.

Campaigns in the portal

A campaign goes the promotional route and runs the duplicate check on its own — once the recipient list is built, it shows you how many it found under the Duplicate message warning heading:

Same number and same text — the campaign always removes these, with no choice offered.
Same number, different text — this one is up to you. Tick Remove duplicate recipients and each number gets a single message; leave it unticked and all of them go out.

In an A/B tested campaign duplicate recipients are always removed, otherwise one person would receive several tested variants and the test result would be worthless.

What to watch out for

The same parameter means two different things. On the transactional route duplicates_check is a switch that protects across requests over time; on the promotional route it selects a method and applies only within one request.
A shared account means a shared window. Several integrations under one wallet can discard each other's messages if they send the same texts to the same numbers.
A discarded message is not sent, so it is neither delivered nor recorded among sent messages.
Check the counts in the response. The promotional route reports no removals — if you compare deliveries against your input list, expect the difference.

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