Recipient List Maintenance

The list-related best practices here are focused primarily on Marketing and bulk emails. Marketing emails are more likely to run into issues with bounces, spam complaints, and other deliverability issues, so having a well-maintained recipient list when sending Marketing email is pivotal to deliverability. Transactional emails are direct messages to a single recipient based on an event but still benefit from these best practices.

The ideal recipient list for a Marketing campaign email is

• Permission-based: recipients have indicated, explicitly via opt-in or business relationship with your organization, that they want to receive content from you
• Clean: Do not purchase lists. Purchased lists often contain invalid email addresses and even spam traps. A combo of high bounce rate, high spam complaint rate, and spam trap hits will have a detrimental effect on deliverability and reputation.
• Not stale: maintaining an engaged list is pivotal, and a list is considered "stale" if they have not been emailed in over 3-6 months. 

Depending on the location of your recipients, different anti-spam legislation may apply to your Marketing mailings. Most legislation contains similar expectations:

• Explicit, verifiable permission (via opt-in or previous business relationship) from the recipient
• Clear and functional unsubscribe mechanism
• Sender identity and subject line should be accurate
• Reply-to address should be valid
• Content should contain relevant information and a physical postal address 

The CAN-SPAM Act was signed into law by the US in 2003, and outlines general guidelines for unsubscribe, content, and sending compliance when sending bulk email to individuals in the United States. CAN-SPAM does not strictly expect permission, and focuses rather on requiring a one-step unsubscribe process to make it easy for unsolicited mail to be opted-out of from the sender.

The Canadian Anti-Spam Legislation (CASL) took effect in July 2014. CASL specifies that all marketing email messages must only be sent to recipients who have given express consent via opt-in. Existing business relationships are considered to have implied consent, as long as the content of the messages is relevant to that relationship and the relationship is recent (within 36 months). In all cases, a means of opting-out (unsubscribing) is required. 

The EU Opt-In Directive has been in place for European Union member states since 2002. In the EU, B2C (business to consumer) rules are stricter than B2B (business to business) rules: B2C always requires strict permission, whereas B2B does not necessarily require explicit opt-in. B2B opt-in expectations are left at the discretion of EU member nations.

Read more:

Litmus Blog: How to Master International Opt-in Requirements

Litmus Blog: The Ultimate Guide to International Email Law (Infographic)