First Interstate Bank: email security grade A

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First Interstate Bank, Billings, Montana, is the 80th largest FDIC-insured US bank by total assets ($26bn). On 4 November 2026 the public email records of firstinterstatebank.com graded A: MX pass, SPF pass, DMARC p=reject, mail handled by Mimecast.

Grade A. Nothing in the records will stop mail. Read by DNS on 4 November 2026; the records are shown as published.

What was found on firstinterstatebank.com

Check	Result	What was published
MX	Pass	`10 us-smtp-inbound-1.mimecast.com`, `10 us-smtp-inbound-2.mimecast.com`. Mail handled by Mimecast
SPF	Pass	`v=spf1 include:spf.mtasv.net include:amazonses.com ~all`. DNS lookups: 2 of 10 allowed; ends ~all
DMARC	Pass	`v=DMARC1;p=reject;rua=mailto:c40dabb26652320@rep.dmarcanalyzer.com;ruf=mailto:c40dabb26652320@for.dmarcanalyzer.com;fo=1;`. Policy p=reject; reports collected (rua= set)
DKIM	Reported, not graded	No key on any of 10 common selectors. This proves nothing: the bank's real selectors may be any name

Where First Interstate Bank ranks

First Interstate Bank is the 80th largest FDIC-insured US bank by total assets, at $26bn as reported to the FDIC (certificate 1105; Billings, Montana). Among the 999 graded banks, First Interstate Bank ranks 67th by grade (ties broken by assets, larger first). In its asset band, $10bn to $100bn, it ranks 37th of 122; among the 7 graded banks in Montana, 2nd. 69.7% of its band and 85.7% of its state graded A.

What this means for the bank

The checker's own notes on each record:

MX, pass: 2 MX records. Replies have somewhere to land.
SPF, pass: One SPF record, ending in ~all (softfail): mail from a server that is not on the list is treated as suspect.
SPF, info: DNS lookups: about 2 of the 10 allowed. This count is an estimate.
DMARC, pass: Policy p=reject: receivers are asked to refuse mail that fails.
DMARC, info: Reports go to c40dabb26652320@rep.dmarcanalyzer.com.
DKIM, info: No DKIM key at the 10 common selectors tried. That does not mean DKIM is missing. Your email provider picks the selector name, and DNS has no way to list them.

What this means if you sell to First Interstate Bank

First Interstate Bank routes inbound mail through Mimecast, a filtering gateway. Expect strict inbound filtering: a message from a sender whose SPF, DKIM or DMARC fails, or whose domain has little sending history, is unlikely to reach a person. Before you send, run your own domain through the email setup checker and publish a policy with the DMARC record generator. For how a bank buys, see the selling to banks playbook.

Check it live

The records above are from 4 November 2026. Run the same check on firstinterstatebank.com now for today's result. The FDIC's record of the bank is at BankFind, certificate 1105.

This page is one of 1,000 in the Bank Email Readiness Index Q4 2026, published 4 November 2026 and re-read every quarter; the next edition is due 2 February 2027. If you work at First Interstate Bank and the records have changed, email moe@roimaxi.com and we will re-check and update this page.

ROI Maximizer is a trading name of M Ventures LTD, registered in England and Wales, company no. 15554493. Registered office: 4 Beau Street, Bath BA1 1QY, United Kingdom. moe@roimaxi.com