Deck (https://www.hellodeck.ai/) is an AI assistant that can be reached by a dedicated email address, capable of automating tasks, following discussion threads and organizing work by projects.

The user chooses a name for their assistant, which then has its own email address.
Deck can summarize a lengthy thread or any other instruction given by reply or forwarding on demand.
Programmed automations can be set up.

Ability to connect applications (Gmail, Outlook, Google Calendar, Google Drive, Slack, Notion, HubSpot, Fireflies, Granola, Docusign) to prepare responses.
No direct response to other recipients of a thread.

Note: access to mailboxes, calendars, documents and contracts involves a fairly large share of data. The site highlights the lack of training of models on user data, but no model is specified.

In free version, standard AI chat, up to 5 scheduled tasks with 10 executions per month, standard assistant configuration, no long memory.
Note: a pro account is offered on a 15-day trial upon registration.