A knowledge base article on why only one active banner is permitted in Email/Newsletter Zones.
Revive Adserver has an Email/Newsletter Zone type, which exists specifically for the purpose of delivering banners as part of an email campaign. The Email/Newsletter Zone only allows one active banner to be linked to the zone at a time.
The reason for this is as follows:
This is why Revive Adserver only allows one banner to be active at a time in Email/Newsletter Zones.