7 Common Mistakes Marketers Make When Building Trade School Contact Lists | EducationDataLists

Mailgun's 2025 State of Email Deliverability research, based on more than 1,000 senders, found that 39% of senders rarely or never conducted email list hygiene. The study also found that 9.4% had purchased a list or scraped the web for email addresses during the previous two years.

Mailgun's newer research shows some improvement: 33% of senders now conduct list hygiene at least monthly and another 29% do so quarterly, but 22% still rarely or never clean their lists.

For trade-school campaigns, hygiene should include:

• Removing hard bounces
• Suppressing unsubscribed contacts
• Identifying duplicates
• Rechecking outdated addresses
• Reviewing role changes
• Segmenting based on engagement
• Monitoring inactive contacts
• Maintaining suppression records

List hygiene is therefore not just a technical email task. It is a contact-data management process.

7. Treating Deliverability as Separate From Database Quality

The final mistake is assuming that once a database has been assembled, deliverability becomes the email platform's problem.

It does not.

Google's current Gmail sender requirements emphasize authentication, unwanted-email prevention, and easy unsubscribing. For senders reaching 5,000 or more Gmail accounts per day, Google requires SPF, DKIM, DMARC, valid DNS configuration, TLS, and one-click unsubscribe for applicable marketing messages. Google also recommends keeping reported spam rates below 0.10% and avoiding 0.30% or higher.

That makes database quality directly relevant to sending performance.

If marketers repeatedly send to irrelevant, inactive, or unwanted contacts, engagement can deteriorate and spam complaints can increase.