Okay, sooner or later someone is going to need to synchronise all those people who registered on your company website with an email service provider to do a bit of marketing. In my case, the latest email provider to come my way is MailChimp. MailChimp is a very popular email service provider, which was used primarily by small businesses who could not afford the typical email giants like Experian and CheetahMail. However, the industry has changed and now they service many major companies.
To do so, you will need to use the MailChimp API. The latest as of the time of writing is v2.0 and can be found here: http://apidocs.mailchimp.com/api/2.0/
On to the tips!
1. Try not to update incrementally using dates
2. Do a full list compare between the MailChimp lists and your own database
3. Re-subscribing requires 2 actions
4. Use 1 or 0 for boolean parameters
5. Remember localisation
6. Remove left and right space paddings and tab characters for email address before uploading or comparing email
7. Do not forget to handle stray emails
8. Use Webhooks to unsubscribe people at real-time
9. Remember to close the loop by unsubscribing people from your database too
10. Keep records of invalid emails – and do something about them