# One connection per sender

> Why BooleanSMTP refuses to save two connections that share a From address, and how to fix it when that happens.

Each From address is used by one connection, active or inactive — a message from that address always
goes out through the connection that owns it.

- Capitals don't matter: `Hello@example.com` and `hello@example.com` are the same address.
- `hello+backup@example.com` is a different address from `hello@example.com`.
- A connection with no From address of its own never conflicts with another one.

## When BooleanSMTP refuses to save a connection

Saving or activating a second connection with an address another one already uses is refused, naming
the connection that owns it. To fix it:

1. Open the connection the message names and change its provider there, or
2. Give one of the two connections a different From address.

## Next steps

- [How a connection is chosen](/sending/)
- [Mailers](/mailers/)
- [Troubleshooting](/troubleshooting/)