Retrieve the per-message reporting totals for a campaign. Each element of campaignMessages corresponds to one message the campaign sent: a single element for a regular campaign, and one element per variation for a split (A/B) campaign, which is the only way to break a split campaign's results down by variation.

The counters are lifetime totals for the message and cannot be constrained to a date range.

This collection is not paginated: every message of the campaign is returned, and limit, offset and meta.total do not apply. The endpoint is read only; POST, PUT and DELETE return 403.