Horizon
Shows events from the Google calendars you connect. Its Google Calendar permissions are read-only.
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Google account access
Horizon and Mail Sifter are privately hosted applications. You choose whether to connect a Google account to each one.
The applications
Mail Sifter
Helps you read, organize, compose, and send mail. With your permission, it can use Gmail and read Google Contacts to suggest recipient addresses. It also supports IMAP and SMTP accounts.
Your choice and control
Horizon and Mail Sifter have separate Google OAuth clients. Each account holder approves access for each application separately. You can remove access in Google Account settings.
The applications store connected-account tokens and working data on the operator’s TrueNAS system. The original Gmail, Calendar, and Contacts data remains with Google. This public website does not receive your connected-account data.