Overview
Bulk Sending refers to the practice of sending a single message to a large group of recipients simultaneously (e.g., newsletters, marketing updates, or holiday announcements).
Because global mail providers are highly sensitive to large volumes of mail, following a structured approach is essential. While Clearbox manages the technical "heavy lifting" of the server infrastructure, your success depends on your sending habits and list management.
1. Planning and List Health
The foundation of a successful bulk campaign is a high-quality recipient list.
- Permission-Based Sending: Only send to individuals who have explicitly "opted-in" to receive your mail. Sending to "purchased" or "scraped" lists is the fastest way to get your domain blacklisted.
- Segmentation: Don't send everything to everyone. Group your recipients by their interests or how often they interact with your mail.
- Consistent Identity: Always use a consistent "From" name (e.g., "Sarah from Clearbox") and a recognizable email address. This builds trust with both your readers and automated spam filters.
2. The "Warm-Up" Phase (Volume Ramping)
If you are using a new domain or have never sent bulk mail before, you must "warm up" your reputation. Sending 10,000 emails on day one will trigger security alerts. Instead, follow a gradual ramp-up schedule:
| Phase | Daily Volume | Target Audience |
|---|---|---|
| Day 1 | 100–200 emails | Your most engaged/recent customers. |
| Day 2 | 300–500 emails | Active users. |
| Day 3+ | Double previous day | Broaden the list as long as "Bounce Rates" remain low. |
Note: If you plan to send extremely large volumes (over 50,000 per month), please contact Alfrolia support. We can assist with a dedicated sending setup tailored to your specific volume needs.
3. Understanding Rate Limits
To ensure that all Clearbox users enjoy high deliverability, we enforce specific "speed limits" on outgoing mail.
- The Mailbox Limit: Each user/mailbox is permitted to send 380 emails per hour.
- Batching Strategy: If you have a list of 1,000 people, do not attempt to send them all at once. Program your software or use a tool to send them in "batches" (e.g., 250 every hour) to stay within the limit and avoid "throttling" (intentional slowing of your mail).
4. Content and Template Best Practices
Spam filters look at the "anatomy" of your email. A professional email should be balanced and transparent.
- The Unsubscribe Link: This is mandatory. Every bulk email must have a clear, easy-to-find link for recipients to opt out.
- Text-to-Image Balance: Avoid sending emails that are just one large image. Filters cannot "read" images and may assume they are hiding spam content. Ensure you have at least a few sentences of plain text.
- Mobile Responsiveness: Most business emails are read on phones. Ensure your templates are "responsive" (they resize automatically for smaller screens).
5. Managing "Bounces" and Complaints
What you do after you send is just as important as the send itself.
- Hard Bounces (Permanent): The email address is invalid or doesn't exist. You must remove these addresses immediately. Repeatedly trying to mail a non-existent address will damage your reputation.
- Soft Bounces (Temporary): The recipient's inbox is full. You can try resending these later, but if they fail three times in a row, it’s best to remove them.
- Complaints: If a user clicks "Report Spam," Clearbox receives a notification. You must remove that user from your list instantly to prevent your domain from being blocked by providers like Gmail or Yahoo.
6. Testing and Monitoring
Before sending to your entire list, perform a "Seed Test":
- Send the email to a few personal accounts (one Gmail, one Outlook, one iCloud).
- Check if they land in the "Inbox" or "Promotions" folder.
- Click every link in the email to ensure they work.
Need Expert Advice on Your Next Campaign?
If you are planning a significant marketing push or are seeing your newsletters land in the spam folder, our Deliverability Team is here to help. We can review your templates and help you build a custom warm-up schedule.