Bulk email sending — dispatching the same message (or personalised variants) to hundreds or thousands of recipients at once — requires careful preparation to avoid deliverability problems, spam complaints, and account suspension. This article covers everything you need to do before your first large send.
What Counts as Bulk Email?
For deliverability and infrastructure purposes, any send to more than 500 recipients in a single batch is considered bulk sending and requires the preparation steps in this guide. Sending to fewer than 500 recipients for routine transactional or notification emails does not require special preparation beyond standard domain authentication.
The Bulk Sending Pre-Flight Checklist
| Area | Requirement | Status Check |
|---|---|---|
| DNS | SPF record published and passing | Check at MXToolbox.com → SPF Lookup |
| DNS | DKIM record published and passing | Check at MXToolbox.com → DKIM Lookup |
| DNS | DMARC record published (p=none minimum) | Check at MXToolbox.com → DMARC Lookup |
| List | All recipients have opted in to receive this type of email | Audit your consent records |
| List | Hard bounces from previous sends have been removed | Check MigoSMTP Delivery Reports for bounced addresses |
| List | List has not been inactive for more than 6 months | If >6 months, run a re-permission campaign first |
| Content | Unsubscribe link included and functional | Click the unsubscribe link in your test send |
| Content | Physical mailing address included in footer | Required by CAN-SPAM |
| Content | Plain-text version included alongside HTML | Check your send payload includes both |
| Quota | Monthly quota has sufficient capacity for the planned send | Check Dashboard → Plan Details → Emails sent |
| Quota | Daily limit can accommodate the send volume within your schedule | Calculate: list size ÷ daily limit = minimum days needed |
| Test | Test email sent and reviewed on desktop and mobile | Use Litmus or Email on Acid for multi-client preview |
| Test | Spam score test performed (below 3.0) | Use mail-tester.com before your first large send |
Step 1 — Validate Your Domain Authentication
Before any bulk send, verify that all three authentication records are correctly published and passing. A failed DKIM or SPF record at scale means thousands of emails landing in spam simultaneously:
# Check SPF nslookup -type=TXT mail.yourcompany.com # Check DKIM nslookup -type=TXT migo._domainkey.mail.yourcompany.com # Check DMARC nslookup -type=TXT _dmarc.mail.yourcompany.com
Or use the online tools at MXToolbox.com for a visual check with plain-language pass/fail results.
Step 2 — Clean Your List Before Sending
- Format validation — remove any addresses that do not match a valid email format. Tools like email-validator.net or a simple regex check catch obvious errors.
- Duplicate removal — deduplicate by email address before uploading. Sending the same email to one person twice from the same campaign generates complaints.
- Bounce history check — export your hard-bounce list from MigoSMTP Delivery Reports and remove all hard-bounced addresses from this send.
- Suppression check — MigoSMTP automatically skips suppressed addresses, but confirm your list does not contain addresses you know have complained previously.
Step 3 — Perform a Spam Score Test
Before sending to your full list, send a test email to mail-tester.com. The service analyses your email for spam signals and gives a score from 1–10. Aim for a score of 8 or higher before sending at scale.
Common factors that lower spam scores:
- Missing SPF, DKIM, or DMARC records
- No plain-text version
- Spam trigger words in subject or body
- Too many links relative to text content
- Broken or suspicious links
- Sending from a domain with poor reputation history
Step 4 — Plan Your Sending Schedule
Large lists that exceed your daily sending limit must be spread across multiple days. Calculate your schedule:
| Your List Size | 10k Plan (500/day) | 20k Plan (1,000/day) | 30k Plan (1,500/day) |
|---|---|---|---|
| 500 recipients | 1 day | 1 day | 1 day |
| 2,000 recipients | 4 days | 2 days | 2 days |
| 5,000 recipients | 10 days | 5 days | 4 days |
| 10,000 recipients | 20 days | 10 days | 7 days |