CURLOPT_MAIL_AUTH(3) Library Functions Manual CURLOPT_MAIL_AUTH(3)
NAME
CURLOPT_MAIL_AUTH - SMTP authentication address
SYNOPSIS
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_MAIL_AUTH, char *auth);
DESCRIPTION
Pass a pointer to a null-terminated string as parameter. This is used to
specify the authentication address (identity) of a submitted message
that is being relayed to another server.
This optional parameter allows co-operating agents in a trusted environ-
ment to communicate the authentication of individual messages and should
only be used by the application program, using libcurl, if the applica-
tion is itself a mail server acting in such an environment. If the ap-
plication is operating as such and the AUTH address is not known or is
invalid, then an empty string should be used for this parameter.
Unlike CURLOPT_MAIL_FROM(3) and CURLOPT_MAIL_RCPT(3), the address should
not be specified within a pair of angled brackets (<>). However, if an
empty string is used then a pair of brackets are sent by libcurl as re-
quired by RFC 2554.
The application does not have to keep the string around after setting
this option.
Using this option multiple times makes the last set string override the
previous ones. Set it to NULL to disable its use again.
DEFAULT
NULL
PROTOCOLS
This functionality affects smtp only
EXAMPLE
int main(void)
{
CURL *curl = curl_easy_init();
if(curl) {
CURLcode res;
curl_easy_setopt(curl, CURLOPT_URL, "smtp://example.com/");
curl_easy_setopt(curl, CURLOPT_MAIL_AUTH, "<secret@cave>");
res = curl_easy_perform(curl);
curl_easy_cleanup(curl);
}
}
AVAILABILITY
Added in curl 7.25.0
RETURN VALUE
curl_easy_setopt(3) returns a CURLcode indicating success or error.
CURLE_OK (0) means everything was OK, non-zero means an error occurred,
see libcurl-errors(3).
SEE ALSO
CURLOPT_MAIL_FROM(3), CURLOPT_MAIL_RCPT(3)
libcurl 2026-07-12 CURLOPT_MAIL_AUTH(3)
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