Maximising Email Deliverability: The Importance of Controlled Campaign Volume

Email deliverability is one of the most critical — and most overlooked — aspects of recruitment marketing. Sending too many emails at once can trigger a cascade of responses from inbox providers: temporary rejections, rate limiting, and, in serious cases, long-term damage to your domain's sending reputation.

Gmail and Outlook in particular are designed to protect their users from spam, and their algorithms are sophisticated. A sudden spike in outbound volume from a domain that doesn't normally send at that scale is a red flag — even if every person on your list has legitimately opted in.

The solution is controlled campaign volume. Roi-AI recommends keeping campaign sends below 20,000 recipients at a time. If your database is larger, split it into multiple batches and send each batch several days apart. This approach maintains sending velocity without triggering volume-based filters, and gives you the opportunity to monitor engagement metrics between sends — allowing you to adjust targeting and content before reaching your entire database.