easy:SetOpt_Mail_RCPT_AllowFails(allow)
allow is get to True, allow RCPT TO command to fail for some recipients.
When sending data to multiple recipients, by default curl will abort SMTP conversation if at least one of the recipients causes RCPT TO command to return an error.
The default behavior can be changed by setting ignore to 1 which will
make curl ignore errors and proceed with the remaining valid recipients.
If all recipients trigger RCPT TO failures and this flag is specified, curl will still abort the SMTP conversation and return the error received from to the last RCPT TO command.