How to Address Mail to Someone at Idaho Maximum Security Institution (IMSI)
Get the format wrong and your letter could be delayed or sent back. IMSI requires a specific four-line layout with their PO Box and Boise ZIP code. Here's exactly how to address it.
IMSI routes all resident mail through a PO Box, so your envelope needs to show "Boise, ID 83707" on the last line - even though the prison itself is located elsewhere. This ensures your letter flows through the correct mail channel.
Use this exact four-line format: [Resident LAST NAME], [IDOC Number] Idaho Maximum Security Institution (IMSI), [Unit Number] PO Box 51 Boise, ID 83707 Here's how it looks filled in: DOE, 123456 Idaho Maximum Security Institution (IMSI), Unit A PO Box 51 Boise, ID 83707
Line one: the resident's last name and IDOC number. This is how staff match your letter to the right person. Line two: the facility name (IMSI) and unit number. Keeping this order helps the mailroom sort quickly and keeps your letter from getting held up.
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- ✓ Send personal letters (not packages) - IMSI residents can receive letters from family and friends, but packages aren’t allowed.
- ✓ Don’t include stamps or stationery - residents with funds are expected to buy envelopes and postage through commissary, and stamps/stationery sent in from the outside won’t be accepted.
- ✓ Photos are allowed with limits - send regular photos only; Polaroids and any photos showing nudity are prohibited.
Note: If you’re sending photos, skip Polaroids and anything with nudity - those won’t make it through.
Once your letter arrives, IMSI staff will open and inspect it for contraband before delivery. If you include something prohibited, your mail may be returned - or turned over to authorities. Stick to a straightforward letter and permitted photos to avoid delays.
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