→ HubSpot mobile app
Custom Channels are not supported in the mobile app inbox. This is a HubSpot limitation, and even HubSpot’s own built-in channels are unavailable there.
→ HubSpot Workflows (for some channels)
Telegram, Instagram, and Slack cannot be used in HubSpot workflows
→ Inbox Sidebar
Proactive message cards cannot be added to the Inbox sidebar due to a HubSpot limitation. However, these cards can still be used on the Help Desk sidebar and contact records, the limitation applies only to the inbox.