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Understand delivery delays
Why a campaign can take time to send, what timings are normal by list size, and when a delay needs investigating.
Campaigns don't always send instantly, and that's usually fine. List size, server load and the receiving providers all affect how long delivery takes. You can watch progress in real time in the Campaign Outbox. This guide explains what's normal and when a delay is worth investigating.
What affects delivery speed
On our side: larger lists take longer to process, as do busy, high-volume sending periods.
On the receiving side: recipient servers often throttle incoming mail, different providers accept at different rates, peak hours are slower, and anti-spam analysis adds a little processing time.
What's normal
- Small lists (under 1,000) - usually delivered within minutes.
- Medium lists (1,000-10,000) - anywhere from 30 minutes to a few hours.
- Large lists (10,000+) - can take several hours depending on conditions.
Keep it moving
Authenticated domains often get priority, clean low-bounce lists process faster, and avoiding peak hours helps. Watch the Outbox so you spot any problem early.
Troubleshooting
Stuck in the outbox for hours - check your account isn't under review or suspended, that you haven't hit a sending limit, and look for an error in the status. If it hasn't moved after about four hours, get in touch.
Some recipients got it, others didn't - different providers process at different speeds, and big ones throttle at peak times. Check whether the delayed addresses share a domain, and that they haven't bounced or unsubscribed.
Much slower than usual - compare the list size to past campaigns, check whether you're sending at peak hours, and confirm your authentication is still valid.
Speeding up future sends - send to engaged subscribers first, split large lists into smaller staggered segments, avoid peak hours, and keep your list clean.
If a campaign is genuinely stuck, open a support ticket.