We use the tutors@cccwinternights.org email list to alert each other when we need a substitute tutor for any reason. A tutor will send a message requesting a sub, and hopefully one of the subs will step up to claim that slot, or one of the other permanent tutors will be able to swap. It is unlikely that anyone will email or call you directly to sub. The email list can also be used for other discussion if necessary.
We currently use Slack for this purpose. It's a cloud-based connected hub where teams create, discuss, and organize work from any device. Thus, it offers Windows or Mac apps, available from slack.com as well as iOS and Android phone apps. . If you haven't already received an invitation to the workspace for Winter Nights tutors, send a request to harrym@cccwinternights.org.
tutors.cccwinternights.org - tutors' working info web site
Some site pages are based on these underlying Google Docs or Sheets. To edit the page, you need to edit the doc.
drive.google.com - file storage (owned by each user, can't be owned by a group)
docs.google.com - free word processing, spreadsheet, presentation apps
(from a cccwinternights.org account to your usual email address)
Note that this explanation was written a while ago, so screens may look different.
Use Gear in upper right to access Mail Settings.
Select Forwarding POP/IMAP tab
Select "Add a forwarding address"
Specify the address in the pop up window
Specify whether copies of email should be saved on Winter Nights Google server or only forwarded.
If there is already a forwarding address, click Disable forwarding, and Save Changes. Then go to step 1.
Verify forwarding address, if necessary.
Select Save Changes
Watch this 3-minute screen movie that demonstrates the process. (Note currently talks about mduuc.org, but it applies just the same to cccwinternights.org.)