---
title: "How a connection is chosen"
description: "The four checks BooleanSMTP runs, in order, to pick which connection sends an outgoing email, down to PHP mail as the last resort."
image: "https://booleansmtp.com/docs/og.png"
---

> Documentation Index
> Fetch the complete documentation index at: https://booleansmtp.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# How a connection is chosen

BooleanSMTP checks four things, in order, until one of them names a connection to send through.

1. **A connection the sending code asked for.** Some sends name a connection directly. For example, a
   resend from **Email Logs** reuses the connection that sent the original message. BooleanSMTP uses that
   connection without any further check.
2. **The connection that owns the From address.** Every connection can have its own From address (see
   [One connection per sender](/docs/advanced/one-connection-per-sender/)); if the message's From address
   belongs to one, that connection sends it.
3. **Your Default Connection.** Set **Default Connection**, under **Settings → Delivery & Reliability**, to
   choose which connection handles everything else. If you leave it on **System Default (PHP Mail)**,
   BooleanSMTP uses your primary connection instead. That is your most recently created active connection,
   if you have one.

   ![The Default Connection field on the Settings screen, set to System Default (PHP Mail).](../../../assets/screenshots/settings-default-connection.webp "Default Connection setting")

4. **PHP mail**, WordPress's own way of sending mail, is used when none of the above found a connection.

## Next steps

- [The journey of an email](/docs/learn/how-sending-works/) to step through this order with an interactive diagram.
- [One site, many senders](/docs/advanced/multiple-mailers/) to configure several mailers and compare common routes.
- [One connection per sender](/docs/advanced/one-connection-per-sender/)
- [Fallback and retries](/docs/advanced/fallback-and-retries/)
- [Settings References](/docs/settings/)

Source: https://booleansmtp.com/docs/advanced/how-a-connection-is-chosen/index.mdx