#include <curl/curl.h> CURLcode curl_easy_setopt(CURL *handle, CURLOPT_MAIL_RCPT_ALLLOWFAILS, long allow);
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 1L which will make curl ignore errors and proceed with the remaining valid recipients.
In case when all recipients cause RCPT TO command to fail, curl will abort SMTP conversation and return the error received from to the last RCPT TO command.
CURL *curl = curl_easy_init();
if(curl) {
struct curl_slist *list;
/* Adding one valid and one invalid email address */
list = curl_slist_append(NULL, "person@example.com");
list = curl_slist_append(list, "invalidemailaddress");
curl_easy_setopt(curl, CURLOPT_URL, "smtp://example.com/");
curl_easy_setopt(curl, CURLOPT_MAIL_RCPT_ALLLOWFAILS, 1L);
ret = curl_easy_perform(curl);
curl_slist_free_all(list);
curl_easy_cleanup(curl);
}