Tips for sending to appended email addresses

Return Path does not recommend sending to email addresses acquired through an email appending list service because of the lack of consent, the high risk for receiving a large number of complaints and sending to unknown users or spam traps. Sending email to appended email addresses contributes to a poor sending reputation, can cause your IP address or domain to be listed on blacklists and can hurt deliverability. 

Sending email to recipients without proof of consent may also violate certain international data and privacy laws such as the Canada Anti-Spam Law (CASL) and the EU’s General Data Protection Regulation (GDPR), which could put your company at risk for legal action. 

Should the decision be made to use an email appending service, here are a few tips to reduce the risk of harm to your email program: 

  • Consult your legal counsel for details on U.S. and international spam and privacy laws to determine your risk level for lack of compliance.
  • Research the email appending service vendor’s reputation in the industry to ensure you are getting high quality data. Some appending services make an effort to obtain accurate data, but many appending services use unreliable data collection methods. Be sure to ask any vendors how they obtain the addresses to ensure accuracy.
  • Prior to deployment, run all appended email addresses through a list verification service to weed out bad addresses.
  • Send one email to a recipient requesting consent to send further email. Include a link to your preference center to allow them to choose the type of email and frequency they wish to receive. If the recipient does not give consent, do not send further email.
  • Send from a different IP address to protect your opt-in email stream. Once consent is given, move the recipient to your opt-in email stream and IP address.
  • Track the performance of the appended email addresses to determine quality. If you see a high complaint rate, a large number of unknown users and spam traps, then the data source is likely unreliable.
  • While sending to appended email addresses, check SMTP bounce logs for errors indicating throttling, unknown users and policy blocks. If these addresses are causing deliverability problems, stop sending to them.
  • Test a random sample of addresses to see what reaction you get from the recipients prior to sending to the entire list. Should the results cause any deliverability issues or indicate possible problems, do not send to the remainder of the list.
  • Send to appended email address recipients in small batches spread out over time to help ensure negative metrics are marginalized.


Was this article helpful?
0 out of 0 found this helpful
Have more questions? Submit a request