Max Active Contacts (MAC)

What Is Max Active Contacts?

Max Active Contacts, also referred to as MAC, is a setting that controls how many contacts can be actively worked in a campaign at one time. Think of it as a cap that keeps your outreach running at a pace your inbox limits can support.

For example, if your campaign has a MAC of 6:

• Up to 6 contacts can be active at one time.
• Additional contacts remain in a Pending status.
• Pending contacts are automatically admitted as active contacts complete their campaign activity and capacity becomes available.

MAC allows your campaign to continue working through contacts without exceeding the capacity supported by your connected inboxes.

How to Set Your MAC

When creating a campaign

You do not need to set MAC during the initial campaign setup.

However, if the campaign includes an email step, you must set a MAC and connect at least one inbox before the campaign can start.

Connect will prompt you to complete these settings before launch.

On an active campaign

You can adjust MAC at any time from the campaign settings.

As you move the MAC slider, you will see how the selected value compares with your available inbox capacity. If you are approaching your limit, a tooltip will notify you and provide access to your inbox settings.

Changes take effect immediately, and your active and pending counts will adjust based on the updated value and available capacity.

How MAC Connects to Your Inbox Limits

Your available MAC is based on the combined daily send limits of the inboxes connected to your campaigns.

For example:

• Inbox 1 has a daily limit of 150.
• Inbox 2 has a daily limit of 150.
• The combined daily capacity is 300.

Based on those limits, you could allocate up to 300 active contacts across campaigns using those inboxes.

When multiple campaigns share the same inboxes, the available capacity is divided across those campaigns. Seamless distributes the available capacity as evenly as possible based on which inboxes are connected to each campaign.

Because the same inbox capacity may be shared by several campaigns, increasing the MAC in one campaign can affect the capacity available to another campaign.

How Emails Are Rotated Across Inboxes

When multiple inboxes are connected to a campaign, Seamless automatically rotates email sends across them.

Rather than sending every email from a single inbox, the campaign distributes sends across the connected inboxes to balance the workload.

This helps:

• Keep individual inbox volume at a healthier level.
• Reduce the risk of messages being flagged as spam.
• Protect your sender and domain reputation.
• Increase campaign capacity by distributing sends across multiple inboxes.

For better long-term deliverability, add inboxes and domains as your sending volume grows instead of significantly increasing the volume sent from one inbox

What Does Pending Mean?

A contact appears as Pending when the contact has been added to a campaign but has not yet been admitted as active.

Pending contacts are queued and automatically admitted in order as capacity becomes available.

You can view the number of pending contacts from the campaign overview. A campaign will not be marked as complete until:

• All pending contacts have been admitted.
• All active contacts have completed their campaign activity.

This ensures every eligible contact in the campaign queue is processed.

How Active Slots Are Counted

When an email is sent for a contact, that contact continues to count against your daily campaign capacity for the remainder of the day.

This applies even when the contact:

• Completes the scheduled step.
• Receives a reply.
• Has an email that bounces.
• Is no longer shown in an active campaign status.

The slot remains held because an email was sent and counted toward the inbox’s daily limit.

When the daily sending limits reset the following day, those held slots are released and additional contacts can be admitted.

Example

Assume a campaign has a MAC of 100.

If 80 contacts are currently active and 20 other contacts received an email earlier that day but are no longer active, the campaign has used all 100 available slots for the day.

No additional pending contacts will be admitted until daily capacity resets or additional capacity becomes available.

Campaign Sends vs. Non-Campaign Manual Sends

Daily inbox capacity applies differently to campaign emails and manual emails.

Campaign emails

Campaign sending limits are enforced as a hard limit.

Once a campaign has used the available daily capacity assigned to its connected inboxes, the campaign will not send additional emails that day.

This protects inbox health and prevents campaigns from automatically exceeding the configured daily limits.

Non-campaign emails

Non-campaign emails, including one-off emails or replies sent manually outside of a campaign, are not hard blocked.

When a manual email would exceed your remaining daily capacity, Seamless displays a warning before the email is sent. You can confirm that you still want to proceed.

This gives you visibility into your sending volume without preventing you from sending an important individual message.

What Happens When an Inbox Has No Daily Limit?

When an inbox does not have a daily send limit configured, it can contribute a maximum MAC of 50 to each campaign it is connected to.

For example, if the same no-limit inbox is attached to three campaigns, it can contribute up to 50 active contacts to each campaign. The limit is applied per campaign rather than shared as a total of 50 across all campaigns.

However, configuring an actual daily sending limit is strongly recommended. Sending at an unrestricted volume from a single inbox or domain can increase the risk of:

• Spam filtering.
• Poor sender reputation.
• Domain reputation damage.
• Reduced email deliverability.

For healthier long-term sending, configure realistic daily limits and increase capacity by adding properly managed inboxes and domains.

Important Rules

• Campaigns with email steps require a MAC and at least one connected inbox.
• A campaign is not complete until all pending contacts have been processed.
• Call-only campaigns do not require MAC, but you can set one to limit active contacts.
• Contacts that received an email continue counting against capacity for the rest of the day.
• Inbox capacity may be shared across multiple campaigns.
• Inboxes without a daily limit contribute a maximum MAC of 50 per campaign.
• Changes to MAC on an active campaign take effect immediately.

Best Practices

For the best campaign performance and deliverability:

• Set a realistic daily limit for every inbox.
• Review all campaigns sharing an inbox before increasing MAC.
• Spread sending across multiple inboxes and domains.
• Increase sending volume gradually.
• Monitor pending contacts to understand how quickly contacts are entering the campaign.

Setting MAC correctly helps your campaigns run consistently while protecting your sending reputation and inbox health.