A mailbox unique id is not a subscriber id.

Answer A mailbox unique id is not a subscriber id. RFC 4315 describes IMAP UIDPLUS. The document is RFC 4315, titled Internet Message Access Protocol (IMAP) - UIDPLUS extension. An identifier inside one mailbox is not the identity of a buyer. It points mail software at something inside that mailbox. It does not name a person, and it does not say the person asked for a letter. A column of those identifiers can look like a customer export. You have not been introduced to anyone.

The note that started this: RFC 4315, Internet Message Access Protocol (IMAP) - UIDPLUS extension, RFC 4315.

Sellers paste the column into a pitch and call each row a subscriber. The row cannot leave the mailbox and remain the same fact. Before you compare solo ad pricing, ask what a row identifies. If the honest answer is a mailbox unique id, you are pricing bookkeeping. A price built on that column is a price for a folder feature, not for a letter to people. The list is still unnamed.

That is a fact about mail software or about an old specification. It is not a solo ad price, a rank, or proof that a stranger opted in. A buyer still has to name the list, the sending domain, and the refund line on the order. UIDPLUS fills none of those blanks. A seller who opens with the identifier and never names the list is handing you a public document and calling it a product. Read the document if you want. Pay only for the order.

What does RFC 4315 describe?

RFC 4315 describes IMAP UIDPLUS. The document is RFC 4315, titled Internet Message Access Protocol (IMAP) - UIDPLUS extension. An identifier inside one mailbox is not the identity of a buyer.

The extension is about identifiers a mailbox uses so a client can refer to messages without guessing. Referral is not identity. Inside one mailbox is the boundary. A person is not a permanent id stored in a folder. A seller who matches buyers across offers by these ids is matching mailbox rows. Rows can be deleted, copied, or local to that folder. None of that is a subscriber moving from one product to the next.

Ask for the person in ordinary words. A list name, a sending domain, and a refund line are the words that belong on the order. A mailbox unique id can stay in the software notes. If it is the only stable thing the seller will show, they have not shown a buyer. The refund line should cover an id sold as a subscriber. A careful seller would rather lose the order than rename a mailbox id as a customer.

• The order names people, not mailbox identifiers.
• The seller can say what the id points at.
• The list, the sending domain, and the refund line are named.
• An export of ids is not treated as the subscriber file.

Is a mailbox unique id a subscriber id?

No. A mailbox unique id is not a subscriber id. An identifier inside one mailbox is not the identity of a buyer. It does not follow the person out of that mailbox.

Subscriber is a person word. Identifier is a mailbox word. When a pitch uses them as synonyms, hold the file up against the sentence. The file will show a value that mail software uses inside one mailbox. The sentence will pretend the value is a customer. Pretending is not a list you can rent. Ask which list the person belongs to, and stop if the answer is the id itself.

If you have not paid, do not pay for the column. If you have paid and the subscriber file was a set of mailbox unique ids, the refund line is the next sentence, not a lesson in mail software. On the seller side, say id when you mean an identifier inside one mailbox. Say subscriber only when you can point at a person on a named list. One word for both is how a folder export gets sold as an audience.

Does a mailbox unique id prove the reader opted in?

No. That is a fact about mail software or about an old specification. It is not a solo ad price, a rank, or proof that a stranger opted in.

An identifier has no signup attached to it. It can mark a message a stranger never asked for, and it will look no different. The sameness will not make the stranger yours. It will not hand you a rank, and it will not set a price. Ask who is on the list. Ask which domain sends. Ask what the refund line says when a mailbox unique id was sold as a subscriber, or when the list is not the list you named.

Price the object in your hand. A mailbox unique id is an identifier inside one mailbox. A solo is one letter to someone else's list. Read that difference before you look for best solo ad vendors. Pay for the letter only after the order names the list, the sending domain, and the refund line. An identifier is not the invoice, and it is not the audience.