A plus-tag is not a new person

Answer A plus-tag is not a new person. RFC 5233 describes subaddressing, the habit of adding a tag to the local part of an address, often after a plus sign, so a filter can tell one signup from another. The tag is a label. The mailbox is still one mailbox unless the recipient's system splits it. Do not pay for a list that counted the labels as people.

The note that started this: RFC 5233, Sieve Subaddress Extension, RFC 5233.

Tracking addresses are useful. You sign up for a seller as you+theirbrand@yourdomain and you know who leaked the address when the spam starts. That usefulness is the reader's, not the seller's excuse to clone you. A file with fifty tags and one human is a file of one human. If you buy solo ads, ask how the count was made.

The extension is a Sieve add-on. It lets a script look at the tag and file the message. The base address still identifies the mailbox in the ordinary case. Some providers ignore the tag and deliver to the base. Some let the user route on it. A sender who does not know which is which should not invent a population from the punctuation.

What is a subaddress on an email list?

RFC 5233 describes the common form where a tag is added to the local part, often after a plus sign. The tag can steer a filter. The mailbox underneath can still be one person.

You have seen the shape. name+newsletter@example.com. name+shoes@example.com. The part before the plus is the mailbox. The part after is a note. A careful subscriber uses a fresh note for every brand, which is a gift when the brand misbehaves, because the subscriber can see who sold or leaked that note. It is not a gift of fifty extra people to mail.

Other delimiters exist. The RFC is written so the detail can be separated by a character the site defines. Plus is the one you will actually see. Do not build a superstition that every address containing a plus is a bot, either. A real person uses the tag on purpose. The fraud signal is behavior, not the character. Yesterday's filters and today's tags get confused in sloppy scrubs. A scrub that deletes every plus-address deletes the careful readers and keeps the careless ones.

• The base mailbox is what you count, unless the tags are proven separate.
• A plus sign is not an automatic bot flag.
• A plus sign is not an automatic extra subscriber.
• The quote states how the count was de-duplicated.

Should each plus-tag count as a subscriber on a solo ad?

No. Ten tags on one mailbox are ten labels, not ten people, unless you have evidence the addresses are actually separate. Counting tags as people inflates the file.

Inflation shows up as a bargain. The seller offers a huge list at a small price per address. The addresses are variations. The first send looks fine because one person got ten copies, or because the provider collapsed them and you only reached one. The second send is when the person hits spam ten times, or once, with feeling. Complaint math gets ugly when one human can represent a crowd in the denominator and a single angry click in the numerator, or the reverse, depending on who is doing the counting.

Ask for a count of unique base addresses if the file uses tags. If the seller cannot produce it, they have not looked. You are buying their lack of looking. Solo ad pricing per thousand means nothing if the thousand is a hundred people wearing ten names.

How should a seller treat tagged addresses?

Keep the tag if it is a real tracking label the subscriber chose. Do not sell a file of tags as a file of humans. Ask which address receives the mail when the tag is ignored.

Keeping the tag is respectful. The subscriber used it so they could manage you. Stripping it can break the filter they wrote and dump you into a pile they did not choose. Collapsing tags only for the invoice, while still sending every variant, is the dishonest middle. Send the address they gave you. Count the human once in any claim about how many people you reach.

RFC 5233 is a small extension about a small piece of punctuation. The punctuation is not a person. Write the count in humans before the wire goes out.