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Secure Mail Support

First Interstate Bank has partnered with Mimecast to communicate securely with you by email. Secure mail transmits encrypted messages that only authorized recipients can access.

Secure Mail Portal

A recipient of a Registered Envelope must create a password with Secure Mail (free of charge) for opening encrypted messages. When you receive your first Secure Mail, another email with an initial password will arrive from

Any Registered Envelopes you receive after this point will contain a link to our Secure Mail Portal. This portal will contain any secure messages received in the last 90 days. In addition, you can reply securely or compose a new secure mail to any bank employee. Secure messages will expire after 90 days.