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Deliverability and Inbox Placement

Overview​

Deliverability is about whether the email you send gets into people’s inboxes (not their spam folders). This page is written for non-technical users — if any step sounds confusing, you can copy/paste the instructions or contact Alfrolia support and we’ll help. Clearbox manages the sending servers for you; most settings you need to check are simple (authentication, message content, and how you manage your recipient list).

Key concepts​

  • Authentication: SPF, DKIM, DMARC
  • Reputation: sending domain and provider reputation (Alfrolia manages sending infrastructure and IPs on your behalf)
  • Engagement: opens, clicks, replies
  • Bounce handling: hard vs soft bounces
  • Feedback loops: complaints and unsubscribes

Common problems and solutions​

1) Messages marked as spam​

Symptoms:

  • Recipients report mail in spam/junk
  • Low open rates

Checks & fixes:

  • Verify SPF, DKIM and DMARC are correctly configured (see Email authentication guide).
  • Check message content: avoid spammy phrases, excessive links or large images.
  • Ensure you send to opted-in recipients and provide clear unsubscribe methods.
  • Review complaint rates and remove high-complaint recipients.

2) High bounce rates​

Symptoms:

  • Many hard bounces
  • Repeated temporary failures

Checks & fixes:

  • Clean your mailing lists and remove invalid addresses.
  • Handle bounces programmatically: treat 4xx (temporary) differently from 5xx (permanent) and remove permanent bounces.
  • Monitor SMTP response codes in delivery logs.

3) Low inbox placement for bulk campaigns​

Recommendations:

  • Ramp up sending volume gradually when you start large campaigns or a new sending domain. If you'd like hands-on help, contact Alfrolia support — we can assist with volume ramping and any dedicated sending setups.
  • Segment recipients and prioritize engaged users.
  • Use a consistent 'From' address and subdomain for mailing campaigns.

4) Authentication failures​

Symptoms:

  • DKIM or SPF failures in message headers
  • DMARC reports showing failures

Checks & fixes:

  • Ensure SPF record includes Clearbox sending servers (check include: values).
  • Verify DKIM public key is published and the selector matches your sending domain.
  • Use DMARC policy (p=none/quarantine/reject) and monitor reports before enforcing.

5) Sending rate limits and throttling​

Clearbox enforces rate limits to protect reputation. For bulk and marketing emails, Clearbox enforces a per-mailbox limit of 380 emails per mailbox/user per hour; exceeding this limit can lead to throttling or temporary deferral of messages. If you see throttling:

  • Spread sending using background jobs and retry with backoff.
  • Coordinate campaigns so they don't peak concurrently.
  • Contact Alfrolia support if you need a higher sending throughput or have a time-sensitive campaign.

Monitoring and tools​

  • Use Clearbox delivery logs and bounce reports to investigate issues.
  • Set up DMARC aggregate reports to monitor authentication.
  • Implement monitoring on complaint rates and unsubscribe logs.

Best practices​

  • Authenticate all sending domains
  • Keep list hygiene routines running
  • Provide clear unsubscribe flows
  • Monitor metrics and set alerts for sudden changes

If problems persist, open a support ticket and include message IDs, timestamps, and SMTP logs to help our team investigate.