diff --git a/docs/libcurl/curl_easy_setopt.3 b/docs/libcurl/curl_easy_setopt.3
index 4d2a22e0b..58564a6f0 100644
--- a/docs/libcurl/curl_easy_setopt.3
+++ b/docs/libcurl/curl_easy_setopt.3
@@ -1850,6 +1850,9 @@ as a long. See also \fICURLOPT_INFILESIZE_LARGE\fP.
 For uploading using SCP, this option or \fICURLOPT_INFILESIZE_LARGE\fP is
 mandatory.
 
+When sending emails using SMTP, this command can be used to specify the
+optional SIZE parameter for the MAIL FROM command. (Added in 7.23.0)
+
 This option does not limit how much data libcurl will actually send, as that
 is controlled entirely by what the read callback returns.
 .IP CURLOPT_INFILESIZE_LARGE