Definition
Parallel and sequential sending are two approaches to delivering an email campaign. A parallel send delivers the campaign to the whole list at effectively the same time, while a sequential send staggers delivery across the audience in ordered waves over a period.
The choice affects traffic, server load and delivery behaviour. Parallel sending is simpler and feels immediate but can create a large burst. Sequential sending spreads volume, smooths throughput and lets you observe early response before the full audience is mailed.
Parallel vs Sequential
| Factor | Parallel Send | Sequential Send |
|---|---|---|
| Delivery | All at once | In staged waves |
| Throughput | Burst | Smooth |
| Early feedback | Late | Early |
| Server/analytics strain | Higher | Lower |
Each suits different situations.
When Parallel Sending Fits
- Immediate campaigns: Breaking news or urgent offers.
- Reach matters fast: The audience wants the email now.
- Simple volume: Delivery infrastructure handles the burst.
When Sequential Sending Fits
- High volume: Staggering eases infrastructure and limits.
- Testing response: Learn from the first waves before mailing everyone.
- Traffic control: Spread conversion load over time.
Related Glossary Terms
Account-Based Marketing Email
An account-based marketing email is a highly targeted message sent to a specific organisation or decision-maker group as part of a focused B2B strategy.
Announcement Email
An announcement email is a dedicated campaign that communicates a specific update, milestone, or change to subscribers, from product launches and feature releases to company news and events.
B2B Email Marketing
B2B email marketing targets business professionals and organisations with longer sales cycles, educational content, and relationship-driven campaigns compared to B2C email.
B2C Email Marketing
B2C email marketing focuses on sending targeted promotional and transactional emails to individual consumers, emphasising personalisation, urgency, and direct response.
Behavioral Email
Behavioral email is a message triggered by a subscriber's action, inaction, or engagement pattern, making it more relevant than scheduled broadcast sends.
Behavioral Segmentation
Behavioral segmentation is the practice of grouping subscribers based on their actions, such as opens, clicks, purchases, browsing and engagement patterns.
Frequently Asked Questions
A parallel send delivers an email campaign to the whole list at effectively the same time. It is immediate and simple but creates a large burst of volume and traffic.
A sequential send staggers delivery across the audience in ordered waves over a period. It spreads volume, smooths throughput and lets you observe early response before mailing the full list.
It depends. Parallel is immediate and simple and suits urgent, time-sensitive campaigns. Sequential eases high volume, reduces server strain and provides early feedback that allows adjustments. Choose based on urgency, volume and delivery constraints.
Yes. A common approach is a controlled rollout: deliver in a series of waves (sequential) but with enough spread to manage volume, while keeping the campaign timely enough to feel immediate. The right mix balances urgency with control.