Email delivered hours after journey completion (retryCount = 0)

Hi team, I’m trying to understand an unexpected delivery timing behavior.

Scenario

• The journey started on 01/28/2026 at 16:23
• Profile entered the journey and completed the email node at 01/28/2026 17:14.
• However, the email was actually received by the user on 01/29/2026 at 06:15 (next day).

Observations

• In ajo_message_feedback_event_dataset, the feedbackStatus = sent
• retryCount = 0
• No failure reason or exclusion reason is present.
• This was a Journey email, not a Campaign.
• The journey starts with a Read Audience of ~1M profiles.
• The reading rate is set to 5,000 profiles per second.

Question

Given that:

• the profile finished the journey node on 01/28,
• the message shows sent with retryCount = 0,
• and there are no failures or retries,

why would the actual email delivery occur many hours later (next morning)?

Could this be related to:

• internal message queueing or batching?
• journey scale / audience size?
• MTA or deliverability throttling handled by Adobe?
• deferred execution even when retryCount = 0?

Any clarification on how send time vs. delivery time is handled internally in this type of high-volume journey would be greatly appreciated.

Thanks in advance!