To archive mail from your mail server to Vaultastic, simply add journaling or mail routing rules to forward a copy of incoming and outgoing mail to the corresponding user id on the vaultastic domain.
If your primary domain is acmecorp.com, and you wish to archive for firstname.lastname@example.org, then the journaling rule should send a copy of all mail received and sent by email@example.com to firstname.lastname@example.org.
In case you have additional queries or need assistance, raise a ticket to the Mithi Support team.
Vaultastic does not support email archiving for email ids hosted on public email networks such as Yahoo, Gmail, Rediff etc.
Vaultastic supports connectors for your domains hosted on GSuite/Gapps, O365, Hosted Exchange etc.