How invitations are batched and sent

Overview#

Tantra does not send every calendar invitation at once. It adds your contacts to the event a batch at a time, spread over several days. This is deliberate. Adding a large group of attendees in one burst can trip Google's own limits and land invitations in spam. Batching keeps delivery steady and safe.

This is the single most important thing to understand about calendar campaigns: a campaign with a large list takes days to finish sending, and that is by design.

How it works#

When you launch, Tantra creates the calendar event first, with no attendees, so no invitation goes out yet. Then it builds a distribution plan, which is the queue of attendees waiting to be added.

From there, invitations go out in batches:

1. Tantra adds a batch of up to 200 attendees to the event.
2. The moment attendees are added, Google emails them the invitation.
3. The next batch is scheduled for 24 hours later.
4. A background process checks every 5 minutes for batches that are due and sends them.

So the pattern is one batch of up to 200 invitations, then a 24 hour wait, then the next batch, and so on until the list is done. Adding attendees is the exact step that triggers Google to send the invite.

Within a single batch, Tantra adds attendees in smaller chunks of up to 50 per request, with a short pause of about 10 seconds between chunks, to stay within a safe sending rate for each mailbox.

Where the first batch happens#

The first batch of each event is sent as soon as you start the campaign. Every batch after that is handled by the background process on its schedule. If you scheduled the campaign for a future time, the first batch waits until that time arrives.

How the audience is split#

Before batching, Tantra splits your contacts across the senders you selected, in proportion to each sender's per-day figure. Each sender then works through its own share in batches. Using more senders spreads the audience wider, but each sender still batches its own portion over time.

Field reference#

What happens next#

Right after launch, the first batch for each event goes out, so your earliest invitations arrive within minutes. Watch the Sent column on the Campaigns list climb as batches complete, while Not Sent shows who is still queued.

Each following day, the next batch is added and more invitations arrive. A campaign of several hundred or several thousand contacts therefore spans multiple days. The status stays Active while batches remain, and moves to Completed once every batch is done. See Calendar campaign statuses explained.

You do not need to keep the page open. Batching runs in the background on its own schedule.

Best practices#

• Plan your event date with batching in mind. If your list is large, start early so invitations finish well before the event.
• Add more senders for large lists so each mailbox carries a smaller share.
• Let the schedule run. There is no need to force or refresh it.

Common mistakes#

• Expecting all invitations at launch. Only the first batch of each event sends immediately.
• Reporting a stalled campaign when it is simply waiting for the next 24 hour batch.
• Setting an event date too close to launch for a large list, so later batches would land after the event.

Troubleshooting#

FAQ#

Why does my campaign take days to send?#

Invitations go out in batches of up to 200, one batch every 24 hours. A large list therefore spans several days. This protects deliverability.

How many invitations go out per day per event?#

Up to 200 attendees are added per batch, and one batch is scheduled every 24 hours per event.

What actually sends the invitation email?#

Adding attendees to the event does. Google emails each new attendee the moment they are added.

Can I make it send faster?#

Add more senders so the audience is split into smaller shares that send in parallel. The 24 hour batch interval itself is fixed.

Does closing the browser stop sending?#

No. Batching runs in the background on the server, so you can close the page.

Related articles#

• Create a smart calendar campaign
• Calendar campaign statuses explained
• My calendar campaign is not sending invites