Enable IMAP and SMTP on Your Inboxes

Instantly uses IMAP to read each inbox (to find replies and warmup emails) and SMTP to send from it. Check both are turned on for each inbox.

Google Workspace

For your whole organization (do this once):

1. In the Google Admin console, go to Apps > Google Workspace > Gmail > End user access
2. Make sure POP and IMAP access is turned on for all users

For each inbox:

1. Log in to Gmail as that user
2. Select the cog in the top right, then See all settings
3. Select the Forwarding and POP/IMAP tab
4. If you see an option to enable IMAP, select Enable IMAP, then Save Changes. Newer accounts have IMAP turned on already.

Zoho Mail

For each inbox:

1. In the Zoho Mail Admin Console, go to Users and select the user
2. Select Mail accounts (or Mailbox settings)
3. Turn IMAP access on
4. Turn POP access off, as you don't need it
5. Check Outgoing (SMTP) is allowed