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Bulk sending best practices

Overview​

Bulk sending means sending the same message to many people (newsletters, updates, or marketing emails). This page uses plain language and gives step-by-step advice — if anything is unclear, just contact Alfrolia support and we'll walk you through it. The technical parts of sending (servers and IPs) are managed by Alfrolia; your focus should be on who you send to, what you send, and how often.

Planning and segmentation​

  • Send only to opted-in recipients.
  • Segment lists by engagement (active, lapsed, occasional) and target high-engagement groups first.
  • Use consistent From addresses and clear identity (company name and SPF/DKIM aligned domain).

Warm-up and volume ramping​

  • If you're starting bulk sending or using a new sending domain, increase your sending volume gradually. Example schedule you can follow if you're self-managing:
    • Day 1: 100–200 emails to your most engaged users
    • Day 2: 300–500
    • Increase by ~2x per day as long as engagement and complaint rates remain low
  • Monitor bounces and complaints closely during ramp-up.
  • Note: Alfrolia manages the sending infrastructure for you. If you plan very large volumes or want a dedicated sending setup, contact Alfrolia support and we'll help with the warm-up and configuration.

Rate limits & batching​

  • Respect Clearbox sending rate limits; spread sends over multiple connections and use exponential backoff for retries.
  • Clearbox enforces a per-mailbox limit of 380 emails per mailbox/user per hour for bulk and marketing sends; exceeding this limit may cause throttling or temporary deferral of messages. If you require higher throughput for legitimate business needs, contact Alfrolia support to discuss options.
  • Use small batch sizes and queue sends in background jobs.

Templates and content​

  • Avoid spammy language, excessive images, and missing unsubscribe links.
  • Use a readable HTML structure and inline CSS; ensure mobile responsiveness.
  • Include text-only alternatives and valid unsubscribe headers/links.

Bounce handling​

  • Treat hard (5xx / permanent) bounces as grounds to remove or suppress addresses.
  • Soft (4xx / temporary) bounces should be retried with an increasing backoff; log failures for later cleanup.

Suppression lists​

  • Maintain suppression lists for unsubscribes, hard bounces, and repeated complaints.
  • Do not re-send to suppressed addresses.

Handling complaints and feedback loops​

  • Monitor complaint rates (ISP feedback loops) and remove complaining recipients immediately.
  • Investigate causes (content, frequency, list acquisition practices).

Testing & verification​

  • Send test campaigns to seed lists across major providers (Gmail, Outlook, Yahoo) and inspect headers for SPF/DKIM/DMARC pass and spam signals.
  • Use seed list services and inbox placement tools for more accurate insight.

Monitoring​

  • Track delivery rates, bounces, complaints, opens, clicks, and engagement metrics.
  • Create alerts for sudden spikes in bounces or complaints.

Common issues and fixes​

  • Sudden spike in bounces: check recent list imports and validate addresses.
  • High complaint rate after a campaign: review content and timing; pause subsequent sends and investigate.
  • Slow delivery: check rate-limiting and retry behavior; examine sending queue and worker logs.

If you plan to send very large volumes, contact Alfrolia support for dedicated IPs and tailored advice.