PayPal Holdings, Inc. is an American company operating a worldwide online payments system that supports online money transfers and serves as an electronic alternative to traditional paper methods like cheques and money orders.

The company operates as a payment processor for online vendors, auction sites, and other commercial users, for which it charges a small fee in exchange for benefits such as one-click transactions and password memory.

Simple Mail Transfer Protocol (SMTP) is an Internet standard for electronic mail (email) transmission.

First defined by in 1982, it was last updated in 2008 with Extended SMTP additions by, which is the protocol in widespread use today.

An open mail relay is an SMTP server configured in such a way that it allows anyone on the Internet to send e-mail through it, not just mail destined to or originating from known users.

This used to be the default configuration in many mail servers; indeed, it was the way the Internet was initially set up, but open mail relays have become unpopular because of their exploitation by spammers and worms.

Many relays were closed, or were placed on blacklists by other servers.

Email spam, also known as junk email, is a type of electronic spam where unsolicited messages are sent by email.

Email marketing is the act of sending a commercial message, typically to a group of people, using email.

In its broadest sense, every email sent to a potential or current customer could be considered email marketing.

It usually involves using email to send advertisements, request business, or solicit sales or donations, and is meant to build loyalty, trust, or brand awareness.

Marketing emails can be sent to a purchased lead list or a current customer database.

The term usually refers to sending email messages with the purpose of enhancing a merchant's relationship with current or previous customers, encouraging customer loyalty and repeat business, acquiring new customers or convincing current customers to purchase something immediately, and sharing third-party ads.