What is plus-addressing and tagging?

Plus addressing allows a sender to add a plus sign and tag after the mailbox name. For example captain+newsletter@tidalmail.com still routes to captain@tidalmail.com while letting the user sort or filter mail.

This technique is known as sub addressing and has existed for decades. Its usefulness is often undermined by poorly written web forms that reject the plus sign even though it has been valid since the earliest email specifications.

This is useful for tracking signup sources or creating temporary aliases. It is the same ship sailing with different flags depending on the voyage.