Outbound calls from your Aircall number may sometimes appear as Spam, Spam Likely, or Scam Likely on the recipient's caller ID, or may be blocked entirely. This article explains why spam flagging occurs, how to detect it, and what you can do to reduce the likelihood of your numbers being flagged.

What is a spam call

A spam call is a call made from a number that has been flagged as suspicious by any of the following:

  • Phone carriers
  • Phone operating systems such as iOS or Android
  • Phone apps such as WhatsApp, Telegram, or Viber

When a number is flagged, recipients may see warnings on their caller ID or may not receive the call at all.

Why spam flagging and call blocking exist

Spam flagging is designed to protect consumers against:

  • Robocalling: High-volume, short-duration calls originating from a single number.
  • Illegal calls: Calls that violate local or international regulations.
  • Unwanted calls: Calls made without the recipient’s consent.

To reduce these types of calls, regulators and major phone carriers require caller ID authentication and apply filtering rules based on calling behavior.

Sources of spam flagging and call blocking

Spam flags can originate from several different sources.

Flagging by consumers

  • Consumers can report numbers to their carrier as suspicious or spam.
  • Consumers may use apps such as Nomorobo or Robokiller to identify or block spam calls.
  • Consumers can block all calls from numbers not included in their contacts or an allow list.

Flagging by carriers

  • Receiving carriers, and in rare cases the originating carrier, may flag or block numbers based on call patterns.
  • Common triggers include high call volumes or a high percentage of unanswered calls.

Flagging by operating systems or apps

Some devices and apps maintain their own spam databases, including: Truecaller, Hiya, Whoscall, Robokiller, Youmail, CallApp.

These services may flag numbers automatically based on reported activity or public complaint data.

How spam is identified by consumers

Most smartphones include built-in systems or third-party integrations that analyze incoming calls against known databases. Consumers can also manually install apps that display spam warnings or rely on public complaint databases such as: Truecaller, Hiya, Whoscall, Robokiller, Youmail, CallApp.

Signals that may trigger spam flagging

Carriers and analytics providers work with third-party networks to analyze calling behavior in real time. They don't publish exact formulas, but the following signals are consistently documented as flagging triggers:

  • High call volume from one number: a large number of calls from a single number in a short period is the strongest spam indicator. Carrier algorithms detect volume spikes as suspicious activity.
  • Low answer rate: a high proportion of unanswered calls signals recipients are rejecting the number. Low answer rate is both a symptom and a cause of further flagging.
  • Short call duration: calls under 20 to 50 seconds are associated with automated or robocalling. Many short or abandoned calls from the same number raise the risk score.
  • Repeated calls to the same number: calling the same recipient multiple times in a short window is a strong spam signal.
  • Consumer complaints: recipients can report numbers directly to their carrier or to spam detection apps. Each complaint increases the risk score in the analytics database.
  • Unregistered numbers: numbers with no established identity in carrier analytics networks are treated as unknown callers and are more likely to be flagged.
  • Low number maturity: numbers with little or no call history carry higher risk. Because spammers constantly rotate through fresh numbers to avoid detection, analytics providers distrust new numbers by default. Early flags on new numbers often resolve naturally as healthy usage builds over time.

Why replacing a flagged number doesn't help

Retiring a flagged number and activating a new one is a common reaction, but it's usually counterproductive. Because spammers constantly cycle through brand-new numbers to evade detection, carrier algorithms treat numbers with no call history as suspicious by default. A replacement number that suddenly receives a burst of outbound calls looks identical to a spam operation starting a new rotation cycle, and may be flagged even faster than the original.

Abandoning an established number also erodes whatever call history and recognition it had built. Reputation builds gradually over weeks or months, and discarding a number means starting from zero.

IMPORTANT:
Aircall does not implement automated number replacement as a spam mitigation strategy. The effective long-term approach is to protect and build a stable number identity over time, through consistent calling behavior, number registration, and, where appropriate, Branded Caller ID.

How Aircall can help

Aircall does not have direct control over spam databases or the removal of spam labels. However, two native features help you understand your number health and reduce the risk of spam flagging.

Number Reputation

Number Reputation is a consumption-based add-on that monitors the daily spam status of each enrolled number directly in the Aircall Dashboard: Healthy, Risk, or Spam with a label category. Status is visible in the number selector when placing a call and in campaign pool configuration, so you can avoid using flagged numbers. Available in the US, Canada, United Kingdom, France, Spain.

Please see Number Reputation: monitor and manage spam labels on your numbers for setup instructions.

Branded Caller ID

Branded Caller ID is a consumption-based add-on that displays your company name and logo on the recipient's screen before they answer. Because your brand identity is validated through the analytics network, carriers may treat your calls as coming from a legitimate, known business, which can reduce the likelihood of being flagged as spam, though this isn't guaranteed. It's most effective when activated proactively, before a spam issue occurs. Available for US, Canada, United Kingdom, France, Spain, numbers.

Please see Branded Caller ID: show your business name on outbound calls for setup instructions.

Important: Neither Number Reputation nor Branded Caller ID can guarantee spam flag removal. Removal decisions are made solely by the relevant carriers or spam detection services. Improving your outbound calling behavior is the most effective long-term fix.

Best practices when calling

Adopting the following best practices can help reduce spam flags and improve call answer rates.

Reduce call volume per number

  • Split call volume across two or three different numbers if you make a large number of outbound calls.
  • Avoid calling the same number multiple times in a single day.

Reduce short and unanswered calls

  • Avoid calling at times that are likely to result in immediate hang-ups.
  • Leave a voicemail explaining who you are and why you are calling.
  • Increase callback rates by clearly sharing your contact details.
  • Make sure your team identifies themselves clearly at the start of each call.

Improve consent and targeting

  • Avoid calling people listed in national Do Not Call registries, such as the US registry or Ofcom (UK).
  • Ensure you have collected consent for calling in advance where required by local regulations.
  • Prioritize calling qualified leads or contacts who have opted in to receive communications.
  • Use a personalized welcome message so returned calls clearly identify your business.
Tip: Carefully choosing the time of day you contact customers can significantly improve answer rates and reduce spam complaints.

Distribute call volume: use your number pool

For campaigns, configure a pool of numbers in your campaign settings so calls are distributed automatically across enrolled numbers, preventing any single one from carrying disproportionate volume.

For Local Presence, make sure you have enough local numbers to match destination area codes effectively. To identify which area codes you need:

  • Export three months of outbound call history and identify the most recurrent destination area codes. This reflects your actual calling territory.
  • For US coverage, prioritize the top metropolitan areas by population as a general reference. A downloadable reference list is available.

If you need to purchase additional numbers to complete your pool:

  • Purchase numbers from Aircall Dashboard → Numbers → Create a number. Regulatory verification may be required for some countries and number types, and can take one to three days.
  • Copy call flow configuration: to replicate the call flow of an existing number, open both numbers in the Aircall Dashboard in the same session and copy widgets from the original to the new number. Widget-by-widget copy is supported. Please see Call flow routing: FAQs.
  • Call flow templates: if multiple numbers share the same routing logic, save it as a template and apply it to new numbers quickly. Please see Using call flow templates.

What to do when a number is flagged

  1. Pause the flagged number, or use it carefully.
    • Remove it from campaign pools and ask agents to manually select a different number.
    • If you have Number Reputation enabled, the reputation badge in the number selector makes healthy numbers easy to spot.
    • Don't delete the number. Deletion is permanent.
    • If you have multiple outbound numbers: pause the flagged one and use another with an established call history while remediation proceeds.
    • If it's your only outbound number: keep dialing at a steady, consistent rate. Steady usage signals legitimate activity to carrier algorithms better than stopping does.
    • Optional: resting a flagged number for 2 to 4 weeks alongside a remediation request can help the label clear, though outcomes vary by carrier and aren't guaranteed.
  2. Check its status with Number Reputation, if you have it set up. The Dashboard shows the label category and the last check date.
  3. Request spam flag removal (optional). The side panel for a flagged number includes a Request remediation button, which opens the analytics provider's remediation form directly. This is handled outside of Aircall, and removal isn't guaranteed. If nothing changes after a few days, contact Aircall Support.
  4. Review and adjust your calling behavior. Remediation without a behavior change is temporary; flags return if the patterns that triggered them don't change. Review call volume, answer rates, call duration, and contact list quality. See Best practices above.
  5. Consider Branded Caller ID to reduce the risk of re-flagging once the label clears. Verified business registration can reduce future false flags, but only if calling behavior is clean. Please see  Branded Caller ID: show your business name on outbound calls.

Helpful resources