Best practices to prevent your outbound calls from being marked as spam

If your outbound calls are being marked as "Spam Likely" or "Potential Fraud," it can significantly reduce answer rates and harm your business communications. Mobile carriers and analytics providers use automated systems to detect suspicious calling patterns, and legitimate businesses can be mislabeled due to call volume, frequency, or reputation signals.

This guide provides best practices to help prevent spam flagging, improve call deliverability, and maintain a positive caller reputation. By following these practices, you can reduce the likelihood of spam labels and thereby increase the chances that customers will answer your calls.

Learn more about why outbound calls may be blocked or tagged as spam.

Behavioral best practices

1. Maintain consistent and compliant calling patterns

• Avoid calling the same number multiple times in a short period.
• Spread outbound calls evenly across your available numbers.
• Do not hang up immediately after a call connects.
• Respect the National Do Not Call Registry and any internal opt-out lists.
• Use local numbers when possible to increase answer rates.
• Avoid mixing call intents—dedicate specific numbers to heavy outbound traffic rather than using the same numbers for multiple purposes.

2. Limit number rotation

• Continuous use of numbers, combined with other best practices, builds a positive reputation over time.
• Avoid frequently adding or replacing numbers to bypass spam flags.
• When new numbers are added, “warm them up” gradually with low call volumes.

3. Use clear and professional call scripts

• Train agents to identify themselves and the business purpose early in the call.
• Encourage longer, meaningful conversations—short calls can appear suspicious.
• When calls go unanswered, leave voicemails by clearly stating your business name and purpose to establish legitimacy.
• Respect local time zones and call only during appropriate hours.

Technical and registration measures

1. Register your business numbers

Register your numbers with major analytics providers to help carriers recognize them as legitimate. You can automate this process using Zoom's Enterprise Registration offering.

Recommended registries include:

• Free Caller Registry (covers multiple carriers)
• Hiya (used by AT&T)
• TNS Call Guardian (used by Verizon)
• First Orion (used by T-Mobile)

Tip: Update your registration every 180 days to maintain accuracy.

2. Use branded calling

Branded calling displays your business name, logo, and call reason on recipients’ mobile screens. This helps increase trust and answer rates, which in turn improves your number reputation.

Note: Branded calling is available through third-party providers and may involve additional costs from those providers.

3. Enable call authentication

Ensure your calls are authenticated under STIR/SHAKEN standards. Authenticated calls are less likely to be blocked or mislabeled by carriers. Learn more on the FCC website.

Note: Customer accounts with Zoom Phone and Zoom Contact Center Native numbers automatically perform call authentication under STIR/SHAKEN standards. Manual authentication is only applicable to BYOC configurations.

Zoom solutions for spam prevention

Zoom offers additional tools to help manage and protect your number reputation:

• Enterprise Spam Registration – Allows businesses to register their numbers directly with carrier partners through Zoom.
• Spam Tag Monitoring & Remediation – Provides active monitoring and automated remediation for numbers flagged as spam.