One connection per sender

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 a second connection with an address another one already uses is refused, naming the connection that owns it. If older data already contains two connections with that address, activating one is refused while the other is active. To fix a duplicate when saving:

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
• Mailers
• Troubleshooting