Email deliverability checklist for sending to US inboxes

US inboxes are dominated by Gmail, Yahoo/AOL (Yahoo Mail), Outlook.com and Apple's iCloud/Hide My Email forwarding - four filtering systems with different thresholds, and only two legal frameworks that actually govern what you send: CAN-SPAM at the federal level, and state laws (California's CCPA, for example) that add data-handling obligations on top.

What CAN-SPAM actually requires

CAN-SPAM is permissive compared with GDPR - no opt-in requirement for commercial email - but it is specific about mechanics:

• A working, honored unsubscribe link, processed within 10 business days of the request.
• No misleading subject lines or "from" names.
• A valid physical postal address in every commercial email.
• Clear identification that the message is an advertisement, if it is one.

CAN-SPAM violations are enforced by the FTC and carry real per-email penalties, but in practice the bigger risk to a sender is mailbox-provider filtering reacting faster than any regulator - a spike in complaints gets you throttled or junked within hours, long before a legal complaint would be filed.

The bulk-sender rules that matter more day to day

Since 2024, Google and Yahoo apply bulk-sender requirements to anyone sending roughly 5,000+ messages a day to their domains:

• SPF and DKIM authentication, both passing.
• A DMARC record published at the sending domain (p=none is enough to qualify, but p=quarantine or reject is stronger).
• One-click unsubscribe (List-Unsubscribe and List-Unsubscribe-Post headers), honored within two days.
• Spam-rate kept under Google's published threshold of 0.30% - a reading from Google Postmaster Tools - with anything under 0.10% considered safe headroom rather than a pass/fail line.

These apply per sending domain, not per campaign, so a single bad send can put every mailbox on that domain at risk.

Metrics worth tracking for a US-focused send

What not to do

• Don't buy or scrape US contact lists. Complaint rates on cold, unconsented lists blow past the 0.30% threshold fast, and recovery from a Gmail-level reputation hit takes weeks.
• Don't localize only the copy and skip the infrastructure. A UK or EU sending domain switching to a US audience still needs its own warm-up curve against Gmail and Yahoo specifically - reputation doesn't transfer between inbox providers.
• Don't treat "delivered" as "inboxed." SMTP accepting a message (250 OK) only means the receiving server took custody of it, not that it reached the inbox.

A worked example: reading a real Postmaster Tools spam-rate window

Google Postmaster Tools reports spam rate as a banded range (e.g. "0.00%-0.10%", "0.10%-0.30%", "0.30%-0.50%+") per day, per domain, with roughly a two-day lag. A domain pushing into the US market for the first time typically sees a pattern like this across its first three weeks:

The jump into the 0.10%-0.30% band in week 2 is not itself a failure - it is the signal to stop increasing volume, re-check which segment is driving complaints, and hold at that volume until the band drops back down before ramping further. Treat 0.30%+ as a stop-sending signal for that segment, not just a number to note.

The address formats that trip up US-bound mail specifically

• Role-based addresses at US B2B domains (info@, sales@, support@) bounce or complain at a higher rate than individual addresses - exclude them from cold outreach lists.
• .us and .gov domains often run stricter inbound filtering than consumer webmail; don't assume a pass at Gmail means a pass at a .gov recipient's own mail gateway.
• Catch-all domains (common at small US businesses) accept mail that would otherwise hard-bounce elsewhere, which can mask list-quality problems until a spam-trap hit shows up weeks later.

MailPilot warms new or returning domains against real Gmail, Outlook and other provider seed inboxes, checks SPF/DKIM/DMARC against what's actually in the DNS, and tracks spam-rate-relevant reputation per mailbox daily - so a push into the US market is measured against the providers that actually decide where the mail lands, not just assumed.