--mail-rcpt-allowfails

When sending data to multiple recipients, by default curl aborts SMTP conversation if at least one of the recipients causes RCPT TO command to return an error.

The default behavior can be changed by passing --mail-rcpt-allowfails command-line option which makes curl ignore errors and proceed with the remaining valid recipients.

If all recipients trigger RCPT TO failures and this flag is specified, curl still aborts the SMTP conversation and returns the error received from to the last RCPT TO command.