Who Is Affected
The bulk sender threshold is 5,000 messages per day to Gmail or Yahoo recipients. This is measured per sending domain, not per account or IP address. Even if you don’t currently send at that volume, following these requirements is good practice. Google and Yahoo have stated they may lower the threshold over time, and the requirements align with industry best practices that benefit all senders.Some requirements (like email authentication) apply to all senders, not just those above the 5,000/day threshold. Only the one-click unsubscribe requirement is specific to bulk senders.
The Three Pillars
Authenticate your email
SPF, DKIM, and DMARC must all pass for your sending domain. This is no longer optional — it is a hard requirement.
Enable easy unsubscribe
Marketing and promotional emails must support one-click unsubscribe via the
List-Unsubscribe header. Unsubscribe requests must be processed within 2 days.Authentication Requirements
All three authentication protocols must pass for your sending domain:| Protocol | Requirement | Lettr Implementation |
|---|---|---|
| SPF | Must pass for your sending domain | Lettr handles SPF via the CNAME verification record |
| DKIM | Must pass with proper domain alignment | Lettr signs all emails with your domain’s DKIM key |
| DMARC | Must have at least a p=none policy | You must add a DMARC TXT record to your DNS |
Verifying Your Authentication
Check your DKIM record:Unsubscribe Requirements
For bulk senders, Google and Yahoo require:| Requirement | Details |
|---|---|
List-Unsubscribe header | Must include an HTTPS URL for unsubscribing |
List-Unsubscribe-Post header | Must support one-click unsubscribe per RFC 8058 |
| Visible body link | An unsubscribe link must be visible in the email body |
| Processing time | Unsubscribes must be honored within 2 days (not 10 like CAN-SPAM) |
Implementation in Lettr
Add thedata-msys-unsubscribe="1" attribute to your unsubscribe link to enable unsubscribe event tracking and proper header generation:
Click tracking must be enabled for the
data-msys-unsubscribe attribute to generate unsubscribe events. Lettr will automatically add the appropriate List-Unsubscribe and List-Unsubscribe-Post headers when this attribute is present.Transactional Email Exception
One-click unsubscribe is only required for marketing and promotional emails. Purely transactional emails (order confirmations, password resets, account alerts) are exempt. However, if your transactional email contains promotional content, it may be classified as commercial and the requirement applies.Spam Rate Requirements
Google measures your spam complaint rate through Gmail’s feedback mechanisms. You can monitor this through Google Postmaster Tools.| Metric | Target | Hard Limit |
|---|---|---|
| Spam complaint rate | Below 0.1% | Must stay under 0.3% |
Monitoring with Google Postmaster Tools
- Go to Google Postmaster Tools
- Add and verify your sending domain
- Monitor the Spam Rate dashboard regularly
- Set up alerts if your rate approaches 0.1%
Reducing Spam Complaints
- Make unsubscribe easy — A visible, one-click unsubscribe is the most effective way to reduce complaints. Recipients who can’t find the unsubscribe link will use the spam button instead.
- Send relevant content — Segment your audience and send content they expect to receive.
- Honor frequency expectations — Don’t email more often than subscribers signed up for.
- Clean your lists — Remove unengaged subscribers who haven’t opened or clicked in 6+ months. See List Hygiene.
- Use double opt-in — Confirm subscriptions to ensure recipients genuinely want your emails.
Additional Requirements
Google and Yahoo also require:| Requirement | Details | Lettr Handling |
|---|---|---|
| Valid forward and reverse DNS | Sending IPs must have proper PTR records | Lettr manages this automatically |
| TLS encryption | Emails must be transmitted over TLS | Lettr uses TLS for all SMTP connections |
| RFC 5322 compliance | Messages must follow email format standards | Lettr constructs compliant messages |
| No Gmail impersonation | Don’t use @gmail.com in your From header | Use your own verified domain |
Compliance Checklist for Lettr Users
Verify your domain in Lettr
Add your sending domain and configure the CNAME and DKIM DNS records. Confirm both show as valid in the dashboard.
Add a DMARC record
Add a TXT record for
_dmarc.yourdomain.com with at least v=DMARC1; p=none; rua=mailto:dmarc@yourdomain.com. See DMARC for details.Set up a tracking domain
Configure a custom tracking domain (e.g.,
track.yourdomain.com) to improve link reputation. See Tracking Domains.Implement unsubscribe links
Add
data-msys-unsubscribe="1" to the unsubscribe link in your email templates. Ensure the link is visible and functional.Register with Google Postmaster Tools
Add your domain at postmaster.google.com and verify ownership to start monitoring spam rates and reputation.
What Happens If You Don’t Comply
Emails rejected with 550 errors
Emails rejected with 550 errors
Gmail and Yahoo will outright reject emails from senders who fail authentication checks. You’ll see
550 5.7.26 or similar errors indicating DMARC or DKIM failure. These rejections appear as hard bounces in Lettr.Emails routed to spam
Emails routed to spam
Even if emails are accepted, they may be automatically placed in the spam folder if your spam complaint rate is too high or your authentication is incomplete.
Temporary rate limiting
Temporary rate limiting
Gmail may temporarily throttle your sending if you’re borderline on compliance. You’ll see increased
email.deferred events as Gmail slows acceptance of your messages.Permanent blocking
Permanent blocking
Persistent non-compliance — especially a consistently high spam complaint rate above 0.3% — can result in your domain being permanently blocked by Gmail or Yahoo. Recovery requires fixing the root cause, reducing volume, and gradually rebuilding reputation.