Klaviyo Throttling: Sending a Large BFCM Campaign on Time

A Black Friday campaign can fail to go out in full within the planned period, or be canceled because the account reached its sending limit. Klaviyo describes these two situations on two separate pages, with two different resend methods. This article keeps them apart, so you know which one applies, in line with our Klaviyo BFCM guide.

TL;DR. Throttling means emails that cannot be sent within the planned period because of volume restrictions. Klaviyo recommends choosing flexible overages or auto-upgrade, and adding one hour between scheduling and send time for every million recipients. A campaign canceled because the account reached its sending limit does not resume on its own after a plan change. In both cases, a segment of people who already received the email, excluded from a clone, avoids duplicates.

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What throttling is

According to Klaviyo, throttling is when some emails cannot be sent in a given time period because of volume restrictions (Klaviyo, understanding email throttling). Klaviyo may occasionally throttle emails for one of these reasons:

• auto-upgrade and flexible overages are disabled, and a campaign exceeds the plan limits;
• the number of recipients is unexpectedly high, with not enough time to send to all of them. The page cites the case where the final recipient count is only known after scheduling, in rare cases of high volume campaigns (for example more than a million) with many included and excluded lists and segments, and the case where more recipients are calculated at send time than at scheduling time.

When Klaviyo detects at scheduling that a campaign exceeds the plan limits and the account cannot send beyond them, an in-app warning appears and the campaign cannot be scheduled. The page specifies that the warning may not appear, for example if many profiles were added between scheduling and sending. It adds that email content has no effect on whether a message is throttled.

The page's best practices

Klaviyo recommends:

• choosing flexible overages or auto-upgrade for a paid email plan. Flexible overages add sending capacity for a one-time fee without changing the base plan. Auto-upgrade moves the account to a higher plan tier;
• adding one hour between scheduling and send time for every million recipients of a campaign. The page's example: 3 million recipients and a 4 p.m. send mean going through the scheduling steps at 1 p.m. or before;
• considering breaking up particularly large sends, for example by recipient time zone or into two lists;
• avoiding the "send now" function for time-sensitive sends of a million or more recipients.

The page adds that preparing a message for a list of this size can take several hours.

In our view, the one-hour-per-million rule mostly concerns very high volume accounts. The page gives no lead time for smaller volumes, and we do not try to extrapolate. For a more modest store, the plan limit is the point that seems most useful to us to check before BFCM. Our BFCM send calendar already sets out the technical checks to plan by phase of the weekend, and our article on send time and Smart Send Time covers scheduling.

Choosing your upgrade preference

A third page describes the upgrade preferences, which decide what happens when the account reaches its plan's usage limits (Klaviyo, how to choose your upgrade preference). Depending on the plan, three options exist:

1. Flexible overages: additional usage for the current billing cycle, for a one-time fee. The account stays on its tier.
2. Auto-upgrade: the account moves up to the next tier at the limit, and stays there until it is downgraded.
3. None, for Email and Mobile Messaging: at the limit, sending for that plan stops until you upgrade, use flexible overages, or the billing cycle renews.

The page specifies that flexing can cost more than upgrading, and recommends comparing the costs shown in the billing preferences. To change the preference, you must be an Owner or Admin, have billing permissions, and have a paid plan that is not billed through a contract. The setting is in Billing > Preferences and takes effect immediately. A failed subscription payment disables auto-upgrade and flexible overages, and a failed auto-upgrade or flexible-overage payment disables the affected option.

If the campaign was throttled

The page suggests manually resending the email to skipped recipients. If the throttling came from the plan size, you must first upgrade the plan. The resend uses the membership of the selected lists and segments when its recipients are determined: it can include people who joined those audiences after the original campaign, as well as those who were skipped. The method:

1. In Audience > Lists & segments, click Create, choose Segment, then define: What someone has done (or not done) > Received Email > At least once over all time > where Campaign Name = [campaign name].
2. In Campaigns, open the three-dot menu of the throttled campaign and choose Clone, with a name and a send date. Keep Single channel if Type is shown.
3. In Send to on the clone, confirm the same lists and segments as the original are selected.
4. In Don't send to, keep the original's exclusions and add the segment created in step 1.
5. Review the content and sending settings, then schedule and send.

If the campaign was canceled because of the account limit

The second page covers recipients skipped because the account reached its sending limit, with a notification that the campaign was canceled for exceeding the monthly sending limit (Klaviyo, how to resend a campaign that exceeded account sending limits). It applies to a single-channel email or SMS campaign. At the limit, Klaviyo can cancel a campaign or skip recipients who exceed the remaining allowance, and the page specifies that this is not limited to A/B tests. A campaign canceled for this reason does not automatically continue if you upgrade your plan afterward.

To see the monthly limit, the page says to click your company name at the bottom left, then Billing. In Overview, the Profiles and emails card (or Emails) shows email usage, and the Mobile messaging card shows SMS usage. To avoid exceeding it, it recommends Automatically upgrade, or Flexible overages if the plan supports them, or a manual upgrade before sending.

The resend method differs from the throttling one:

1. In the Campaigns tab, in list view, open the three-dot menu of the canceled campaign and click Copy ID (the original campaign's message ID).
2. In Lists & segments, create a segment: What someone has done (or not done) > Received Email or Received SMS (the original channel) > at least once > over all time > where Message ID equals the copied ID.
3. Clone the canceled campaign, keeping Single channel. At the Audience step, keep the original audience in Send to, add the segment to Don't send to and keep the other exclusions.
4. Review the content and any A/B test settings, then choose Send now or Schedule.

The difference is that the throttling page filters by campaign name and the limits page by message ID. In our view, a copied ID is less prone to typing errors than a name, but the two pages do not compare the two filters.

Checklist before BFCM

These points are Deliver's advice.

1. The upgrade preference is chosen (flexible overages or auto-upgrade), payment is up to date, and the monthly limit has been read in Billing.
2. The largest campaigns are scheduled with a margin, following the one-hour-per-million rule.
3. Very large sends are split rather than launched with "send now".
4. The name and message ID of each campaign are noted, so the resend segment can be built.
5. Someone knows which resend method applies: by campaign name (throttling) or by message ID (account limits).

FAQ

Does email content influence throttling?

No, according to the page: content has no effect on whether a message is throttled.

How much time should you plan for a very large send?

Klaviyo recommends one hour between scheduling and sending for every million recipients.

Does a campaign canceled because of the account limit resume after a plan change?

No. The page says it does not continue automatically. You need to clone it and exclude those who already received it.

How do you avoid sending twice?

By excluding from the clone the segment of profiles who already received the campaign, by campaign name (throttling) or by message ID (sending limits).

Want an outside view on your send plan? We run Q4 readiness audits, or you can talk directly with the Deliver team.