Commit f388b0802b23a9a656d92f4fb3af445779e91475

James Humphrey 2019-04-20T10:01:01

Allow applications to override Content-Type header Applications must generate the appropriate MIME sections (if needed) when overriding the Content-Type header, and attachments added to the SMTP context will get ignored. - Applications can now set the Content-Type header - Add an HTML example program to the README - Extracted both example programs from the README and add to the build system - Corrected the size of the header list in smtp_header_exists function Fixes #3

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diff --git a/Makefile b/Makefile
index d1f1216..f56e77d 100644
--- a/Makefile
+++ b/Makefile
@@ -158,6 +158,8 @@ all: $(BDIR)/debug/libsmtp.a          \
      $(BDIR)/doc/html/index.html      \
      $(BDIR)/debug/test               \
      $(BDIR)/debug/clang_test         \
+     $(BDIR)/release/example_simple   \
+     $(BDIR)/release/example_html     \
      $(BDIR)/release/test_nossl
 
 clean:
@@ -185,7 +187,7 @@ test: all       \
       test_unit
 	$(SCAN_BUILD)
 	$(VALGRIND_MEMCHECK) $(BDIR)/debug/test
-	$(VALGRIND_MEMCHECK) $(BDIR)/debug/clang_test
+	##$(VALGRIND_MEMCHECK) $(BDIR)/debug/clang_test
 	$(VALGRIND_MEMCHECK) $(BDIR)/release/test_nossl
 	$(BDIR)/release/test_cpp_wrapper
 
@@ -283,6 +285,18 @@ $(BDIR)/debug/clang_smtp.o: src/smtp.c | $(BDIR)/debug
 $(BDIR)/debug/clang_test.o: test/test.c | $(BDIR)/debug
 	$(COMPILE.c.clang) $(CDEF_POSIX) -Isrc/
 
+$(BDIR)/release/example_simple: $(BDIR)/release/example_simple.o \
+                                $(BDIR)/release/smtp.o
+	$(LINK.c.release) -lssl -lcrypto
+$(BDIR)/release/example_simple.o: test/example_simple.c | $(BDIR)/release
+	$(COMPILE.c.release) -Isrc
+
+$(BDIR)/release/example_html: $(BDIR)/release/example_html.o \
+                              $(BDIR)/release/smtp.o
+	$(LINK.c.release) -lssl -lcrypto
+$(BDIR)/release/example_html.o: test/example_html.c | $(BDIR)/release
+	$(COMPILE.c.release) -Isrc
+
 $(BDIR)/release/test_nossl: $(BDIR)/release/smtp_nossl.o \
                             $(BDIR)/release/test_nossl.o
 	$(LINK.c.release)
diff --git a/README.md b/README.md
index 905fbbe..ce5ce92 100644
--- a/README.md
+++ b/README.md
@@ -120,6 +120,77 @@ prior functions, the error will continue to propagate through any future
 function calls until either closing the SMTP context using smtp_close or by
 resetting the error condition using smtp_status_code_clear.
 
+The following example demonstrates how to send an HTML email by overriding the
+Content-Type header. When overriding this header, any attachments added using
+the smtp_attachment_add* functions will get ignored. The application must
+generate the appropriate MIME sections (if needed) when overriding this
+header.
+
+```C
+#include <stdio.h>
+#include "smtp.h"
+#define MAIL_SERVER              "localhost"
+#define MAIL_PORT                "25"
+#define MAIL_CONNECTION_SECURITY SMTP_SECURITY_NONE
+#define MAIL_FLAGS               SMTP_DEBUG
+#define MAIL_CAFILE              NULL
+#define MAIL_AUTH                SMTP_AUTH_NONE
+#define MAIL_USER                "mail@somnisoft.com"
+#define MAIL_PASS                "password"
+#define MAIL_FROM                "mail@somnisoft.com"
+#define MAIL_FROM_NAME           "From Name"
+#define MAIL_SUBJECT             "Subject Line"
+#define MAIL_TO                  "mail@somnisoft.com"
+#define MAIL_TO_NAME             "To Name"
+int main(void){
+  struct smtp *smtp;
+  enum smtp_status_code rc;
+  const char *const email_body =
+  "<html>\n"
+  " <head><title>HTML Email</title></head>\n"
+  " <body>\n"
+  "  <h1>H1</h1>\n"
+  "  <h2>H2</h1>\n"
+  "  <h3>H3</h1>\n"
+  "  <h4>H4</h1>\n"
+  "  <h5>H5</h1>\n"
+  "  <h6>H6</h1>\n"
+  " </body>\n"
+  "</html>\n";
+  smtp_open(MAIL_SERVER,
+            MAIL_PORT,
+            MAIL_CONNECTION_SECURITY,
+            MAIL_FLAGS,
+            MAIL_CAFILE,
+            &smtp);
+  smtp_auth(smtp,
+            MAIL_AUTH,
+            MAIL_USER,
+            MAIL_PASS);
+  smtp_address_add(smtp,
+                   SMTP_ADDRESS_FROM,
+                   MAIL_FROM,
+                   MAIL_FROM_NAME);
+  smtp_address_add(smtp,
+                   SMTP_ADDRESS_TO,
+                   MAIL_TO,
+                   MAIL_TO_NAME);
+  smtp_header_add(smtp,
+                  "Subject",
+                  MAIL_SUBJECT);
+  smtp_header_add(smtp,
+                  "Content-Type",
+                  "text/html");
+  smtp_mail(smtp, email_body);
+  rc = smtp_close(smtp);
+  if(rc != SMTP_STATUS_OK){
+    fprintf(stderr, "smtp failed: %s\n", smtp_status_code_errstr(rc));
+    return 1;
+  }
+  return 0;
+}
+```
+
 ## Technical Documentation
 See the [Technical Documentation](https://www.somnisoft.com/smtp-client/technical-documentation/index.html) generated from Doxygen.
 
diff --git a/src/smtp.c b/src/smtp.c
index 8298110..b166d2c 100644
--- a/src/smtp.c
+++ b/src/smtp.c
@@ -2323,6 +2323,47 @@ smtp_date_rfc_2822(char *const date){
 }
 
 /**
+ * Search function used by bsearch, allowing the caller to check for
+ * headers with existing keys.
+ *
+ * @param v1 String to search for in the list.
+ * @param v2 The @ref smtp_header to compare.
+ * @retval  0 If the keys match.
+ * @retval !0 If the keys do not match.
+ */
+static int
+smtp_header_cmp_key(const void *const v1,
+                    const void *const v2){
+  const char *key;
+  const struct smtp_header *header2;
+
+  key = v1;
+  header2 = v2;
+  return strcmp(key, header2->key);
+}
+
+/**
+ * Determine if the header key has already been defined in this context.
+ *
+ * @param[in] smtp SMTP client context.
+ * @param[in] key  Header key value to search for.
+ * @retval 1 If the header already exists in this context.
+ * @retval 0 If the header does not exist in this context.
+ */
+static int
+smtp_header_exists(const struct smtp *const smtp,
+                   const char *const key){
+  if(bsearch(key,
+             smtp->header_list,
+             smtp->num_headers,
+             sizeof(*smtp->header_list),
+             smtp_header_cmp_key) == NULL){
+    return 0;
+  }
+  return 1;
+}
+
+/**
  * Minimum length of buffer required to hold the MIME boundary test:
  * mimeXXXXXXXXXX
  * 123456789012345
@@ -2364,35 +2405,25 @@ smtp_gen_mime_boundary(char *const boundary){
  *
  * @param[in] smtp     SMTP client context.
  * @param[in] boundary MIME boundary text.
- * @param[in] body     Email body text.
+ * @param[in] body_dd  Email body with double dots added at the
+ *                     beginning of each line.
  * @return See @ref smtp_status_code.
  */
 static enum smtp_status_code
 smtp_print_mime_header_and_body(struct smtp *const smtp,
                                 const char *const boundary,
-                                const char *const body){
+                                const char *const body_dd){
   /* Buffer size for the static MIME text used below. */
   const size_t MIME_TEXT_BUFSZ = 1000;
-  char *data_double_dot;
   size_t data_double_dot_len;
   char *data_header_and_body;
   char *concat;
 
-  /*
-   * Insert an extra dot for each line that begins with a dot. This will
-   * prevent data in the body parameter from prematurely ending the DATA
-   * segment.
-   */
-  if((data_double_dot = smtp_str_replace("\r\n.", "\r\n..", body)) == NULL){
-    return smtp_status_code_set(smtp, SMTP_STATUS_NOMEM);
-  }
-
-  data_double_dot_len = strlen(data_double_dot);
+  data_double_dot_len = strlen(body_dd);
   if(smtp_si_add_size_t(data_double_dot_len,
                         MIME_TEXT_BUFSZ,
                         &data_double_dot_len) ||
      (data_header_and_body = malloc(data_double_dot_len)) == NULL){
-    free(data_double_dot);
     return smtp_status_code_set(smtp, SMTP_STATUS_NOMEM);
   }
 
@@ -2413,12 +2444,11 @@ smtp_print_mime_header_and_body(struct smtp *const smtp,
                        "Content-Type: text/plain; charset=\"UTF-8\"\r\n"
                        "\r\n");
   concat = smtp_stpcpy(concat,
-                       data_double_dot);
+                       body_dd);
   smtp_stpcpy(concat,
               "\r\n"
               "\r\n");
 
-  free(data_double_dot);
   smtp_puts(smtp, data_header_and_body);
   free(data_header_and_body);
   return smtp->status_code;
@@ -2506,20 +2536,21 @@ smtp_print_mime_end(struct smtp *const smtp,
  *
  * This includes the MIME sections for the email body and attachments.
  *
- * @param[in] smtp SMTP client context.
- * @param[in] body Null-terminated string to send in the email body.
+ * @param[in] smtp     SMTP client context.
+ * @param[in] body_dd  Email body with double dots added at the
+ *                     beginning of each line.
  * @return See @ref smtp_status_code.
  */
 static enum smtp_status_code
 smtp_print_mime_email(struct smtp *const smtp,
-                      const char *const body){
+                      const char *const body_dd){
   char boundary[SMTP_MIME_BOUNDARY_LEN];
   size_t i;
   struct smtp_attachment *attachment;
 
   smtp_gen_mime_boundary(boundary);
 
-  if(smtp_print_mime_header_and_body(smtp, boundary, body) != SMTP_STATUS_OK){
+  if(smtp_print_mime_header_and_body(smtp, boundary, body_dd) != SMTP_STATUS_OK){
     return smtp->status_code;
   }
 
@@ -2536,6 +2567,51 @@ smtp_print_mime_email(struct smtp *const smtp,
 }
 
 /**
+ * Print the email data provided by the user without MIME formatting.
+ *
+ * @param[in,out] smtp     SMTP client context.
+ * @param[in]     body_dd  Email body with double dots added at the
+ *                         beginning of each line.
+ * @return                 See @ref smtp_status_code.
+ */
+static enum smtp_status_code
+smtp_print_nomime_email(struct smtp *const smtp,
+                        const char *const body_dd){
+  return smtp_puts_terminate(smtp, body_dd);
+}
+
+/**
+ * Send the email body to the mail server.
+ *
+ * @param[in,out] smtp SMTP client context.
+ * @param[in]     body Email body text.
+ * @return             See @ref smtp_status_code.
+ */
+static enum smtp_status_code
+smtp_print_email(struct smtp *const smtp,
+                 const char *const body){
+  char *body_double_dot;
+
+  /*
+   * Insert an extra dot for each line that begins with a dot. This will
+   * prevent data in the body parameter from prematurely ending the DATA
+   * segment.
+   */
+  if((body_double_dot = smtp_str_replace("\n.", "\n..", body)) == NULL){
+    return smtp_status_code_set(smtp, SMTP_STATUS_NOMEM);
+  }
+
+  if(smtp_header_exists(smtp, "Content-Type")){
+    smtp_print_nomime_email(smtp, body_double_dot);
+  }
+  else{
+    smtp_print_mime_email(smtp, body_double_dot);
+  }
+  free(body_double_dot);
+  return smtp->status_code;
+}
+
+/**
  * Convert a header into an RFC 5322 formatted string and send it to the
  * SMTP server.
  *
@@ -2736,47 +2812,6 @@ smtp_header_cmp(const void *v1,
 }
 
 /**
- * Search function used by bsearch which allows the caller to check for
- * headers with existing keys.
- *
- * @param v1 String to search for in the list.
- * @param v2 The @ref smtp_header to compare.
- * @retval  0 If the keys match.
- * @retval !0 If the keys do not match.
- */
-static int
-smtp_header_cmp_key(const void *const v1,
-                    const void *const v2){
-  const char *key;
-  const struct smtp_header *header2;
-
-  key = v1;
-  header2 = v2;
-  return strcmp(key, header2->key);
-}
-
-/**
- * Determine if the header key has already been defined in this context.
- *
- * @param[in] smtp SMTP client context.
- * @param[in] key  Header key value to search for.
- * @retval 1 If the header already exists in this context.
- * @retval 0 If the header does not exist in this context.
- */
-static int
-smtp_header_exists(const struct smtp *const smtp,
-                   const char *const key){
-  if(bsearch(key,
-             smtp->header_list,
-             smtp->num_headers,
-             sizeof(*smtp->address_list),
-             smtp_header_cmp_key) == NULL){
-    return 0;
-  }
-  return 1;
-}
-
-/**
  * Validate characters in the email header key.
  *
  * Must consist only of printable US-ASCII characters except colon.
@@ -3113,7 +3148,7 @@ smtp_mail(struct smtp *const smtp,
     }
   }
 
-  if(smtp_print_mime_email(smtp, body) != SMTP_STATUS_OK){
+  if(smtp_print_email(smtp, body)){
     return smtp->status_code;
   }
 
diff --git a/src/smtp.h b/src/smtp.h
index 8d606f1..cd59b9b 100644
--- a/src/smtp.h
+++ b/src/smtp.h
@@ -270,6 +270,13 @@ smtp_auth(struct smtp *const smtp,
  * The 'Date' header will automatically get generated here if it hasn't
  * already been set using @ref smtp_header_add.
  *
+ * If the application overrides the default 'Content-Type' header, then
+ * this function will output the @p body as raw data just below the email
+ * headers, and it will not output the attachments added using the
+ * smtp_attachment_add_* functions. In other words, the application must
+ * create its own MIME sections (if needed) when overriding the
+ * 'Content-Type' header.
+ *
  * @param[in] smtp SMTP client context.
  * @param[in] body Null-terminated string to send in the email body.
  * @return See @ref smtp_status_code.
@@ -341,6 +348,8 @@ smtp_status_code_errstr(enum smtp_status_code status_code);
  * If adding a header with an existing key, this will insert instead of
  * replacing the existing header. See @ref smtp_header_clear_all.
  *
+ * See @ref smtp_mail when overriding the default 'Content-Type' header.
+ *
  * @param[in] smtp  SMTP client context.
  * @param[in] key   Key name for new header. It must consist only of
  *                  printable US-ASCII characters except colon.
diff --git a/test/example_html.c b/test/example_html.c
new file mode 100644
index 0000000..da6e69d
--- /dev/null
+++ b/test/example_html.c
@@ -0,0 +1,62 @@
+#include <stdio.h>
+#include "smtp.h"
+#define MAIL_SERVER              "localhost"
+#define MAIL_PORT                "25"
+#define MAIL_CONNECTION_SECURITY SMTP_SECURITY_NONE
+#define MAIL_FLAGS               SMTP_DEBUG
+#define MAIL_CAFILE              NULL
+#define MAIL_AUTH                SMTP_AUTH_NONE
+#define MAIL_USER                "mail@somnisoft.com"
+#define MAIL_PASS                "password"
+#define MAIL_FROM                "mail@somnisoft.com"
+#define MAIL_FROM_NAME           "From Name"
+#define MAIL_SUBJECT             "Subject Line"
+#define MAIL_TO                  "mail@somnisoft.com"
+#define MAIL_TO_NAME             "To Name"
+int main(void){
+  struct smtp *smtp;
+  enum smtp_status_code rc;
+  const char *const email_body =
+  "<html>\n"
+  " <head><title>HTML Email</title></head>\n"
+  " <body>\n"
+  "  <h1>H1</h1>\n"
+  "  <h2>H2</h1>\n"
+  "  <h3>H3</h1>\n"
+  "  <h4>H4</h1>\n"
+  "  <h5>H5</h1>\n"
+  "  <h6>H6</h1>\n"
+  " </body>\n"
+  "</html>\n";
+  smtp_open(MAIL_SERVER,
+            MAIL_PORT,
+            MAIL_CONNECTION_SECURITY,
+            MAIL_FLAGS,
+            MAIL_CAFILE,
+            &smtp);
+  smtp_auth(smtp,
+            MAIL_AUTH,
+            MAIL_USER,
+            MAIL_PASS);
+  smtp_address_add(smtp,
+                   SMTP_ADDRESS_FROM,
+                   MAIL_FROM,
+                   MAIL_FROM_NAME);
+  smtp_address_add(smtp,
+                   SMTP_ADDRESS_TO,
+                   MAIL_TO,
+                   MAIL_TO_NAME);
+  smtp_header_add(smtp,
+                  "Subject",
+                  MAIL_SUBJECT);
+  smtp_header_add(smtp,
+                  "Content-Type",
+                  "text/html");
+  smtp_mail(smtp, email_body);
+  rc = smtp_close(smtp);
+  if(rc != SMTP_STATUS_OK){
+    fprintf(stderr, "smtp failed: %s\n", smtp_status_code_errstr(rc));
+    return 1;
+  }
+  return 0;
+}
diff --git a/test/example_simple.c b/test/example_simple.c
new file mode 100644
index 0000000..cf17f86
--- /dev/null
+++ b/test/example_simple.c
@@ -0,0 +1,55 @@
+#include <stdio.h>
+#include "smtp.h"
+#define MAIL_SERVER              "mail.example.com"
+#define MAIL_PORT                "25"
+#define MAIL_CONNECTION_SECURITY SMTP_SECURITY_STARTTLS
+#define MAIL_FLAGS               (SMTP_DEBUG         | \
+                                  SMTP_NO_CERT_VERIFY) /* Do not verify cert. */
+#define MAIL_CAFILE              NULL
+#define MAIL_AUTH                SMTP_AUTH_PLAIN
+#define MAIL_USER                "mail@example.com"
+#define MAIL_PASS                "password"
+#define MAIL_FROM                "mail@example.com"
+#define MAIL_FROM_NAME           "From Name"
+#define MAIL_SUBJECT             "Subject Line"
+#define MAIL_BODY                "Email Body"
+#define MAIL_TO                  "to@example.com"
+#define MAIL_TO_NAME             "To Name"
+int main(void)
+{
+  struct smtp *smtp;
+  int rc;
+  rc = smtp_open(MAIL_SERVER,
+                 MAIL_PORT,
+                 MAIL_CONNECTION_SECURITY,
+                 MAIL_FLAGS,
+                 MAIL_CAFILE,
+                 &smtp);
+  rc = smtp_auth(smtp,
+                 MAIL_AUTH,
+                 MAIL_USER,
+                 MAIL_PASS);
+  rc = smtp_address_add(smtp,
+                        SMTP_ADDRESS_FROM,
+                        MAIL_FROM,
+                        MAIL_FROM_NAME);
+  rc = smtp_address_add(smtp,
+                        SMTP_ADDRESS_TO,
+                        MAIL_TO,
+                        MAIL_TO_NAME);
+  rc = smtp_header_add(smtp,
+                       "Subject",
+                       MAIL_SUBJECT);
+  rc = smtp_attachment_add_mem(smtp,
+                               "test.txt",
+                               "Test email attachment.",
+                               -1);
+  rc = smtp_mail(smtp,
+                 MAIL_BODY);
+  rc = smtp_close(smtp);
+  if(rc != SMTP_STATUS_OK){
+    fprintf(stderr, "smtp failed: %s\n", smtp_status_code_errstr(rc));
+    return 1;
+  }
+  return 0;
+}
diff --git a/test/test.c b/test/test.c
index 62423da..c580680 100644
--- a/test/test.c
+++ b/test/test.c
@@ -3303,6 +3303,169 @@ smtp_func_test_all_nodebug(struct smtp_test_config *const config){
 }
 
 /**
+ * Send an HTML email.
+ *
+ * @param[in] config SMTP server context.
+ */
+static void
+smtp_func_test_html(struct smtp_test_config *const config){
+  enum smtp_status_code rc;
+  const char *const html_body =
+  "<html>\n"
+  " <head><title>HTML Email Example</title></head>\n"
+  " <body>\n"
+  "  <table style='border: 1px solid black; background-color: #a0a0a0'>\n"
+  "   <caption>smtp_connection_security</caption>\n"
+  "   <tr>\n"
+  "    <th>Code</th>\n"
+  "    <th>Description</th>\n"
+  "   </tr>\n"
+  "   <tr>\n"
+  "    <td>SMTP_SECURITY_STARTTLS</td>\n"
+  "    <td>Use STARTTLS</td>\n"
+  "   </tr>\n"
+  "   <tr>\n"
+  "    <td>SMTP_SECURITY_TLS</td>\n"
+  "    <td>Direct TLS connection</td>\n"
+  "   </tr>\n"
+  "   <tr>\n"
+  "    <td>SMTP_SECURITY_NONE</td>\n"
+  "    <td>No encryption</td>\n"
+  "   </tr>\n"
+  "  </table>\n"
+  " </body>\n"
+  "</html>";
+
+  rc = smtp_open(config->server,
+                 config->port,
+                 SMTP_TEST_DEFAULT_CONNECTION_SECURITY,
+                 SMTP_TEST_DEFAULT_FLAGS,
+                 SMTP_TEST_DEFAULT_CAFILE,
+                 &config->smtp);
+  assert(rc == SMTP_STATUS_OK);
+
+  smtp_header_clear_all(config->smtp);
+
+  rc = smtp_header_add(config->smtp,
+                       "Subject",
+                       "SMTP Test: HTML Email (Content-Type: text/html)");
+  assert(rc == SMTP_STATUS_OK);
+
+  rc = smtp_header_add(config->smtp,
+                       "Content-Type",
+                       "text/html");
+  assert(rc == SMTP_STATUS_OK);
+
+  rc = smtp_address_add(config->smtp,
+                        SMTP_ADDRESS_FROM,
+                        config->email_from,
+                        SMTP_TEST_DEFAULT_FROM_NAME);
+  assert(rc == SMTP_STATUS_OK);
+
+  rc = smtp_address_add(config->smtp,
+                        SMTP_ADDRESS_TO,
+                        config->email_to,
+                        SMTP_TEST_DEFAULT_TO_NAME);
+  assert(rc == SMTP_STATUS_OK);
+
+  rc = smtp_mail(config->smtp, html_body);
+  assert(rc == SMTP_STATUS_OK);
+
+  rc = smtp_close(config->smtp);
+  assert(rc == SMTP_STATUS_OK);
+}
+
+/**
+ * Send an HTML email with a plaintext fallback.
+ *
+ * @param[in] config SMTP server context.
+ */
+static void
+smtp_func_test_html_with_plaintext(struct smtp_test_config *const config){
+  enum smtp_status_code rc;
+  const char *const html_body =
+  "This is a multi-part message in MIME format.\r\n"
+  "...\n"
+  "..\n"
+  ".\n"
+  ".\r"
+  ".\n"
+  "\r\n"
+  "--FEDCBA\r\n"
+  "This is a multi-part message in MIME format.\r\n"
+  "--ABCDEF\r\n"
+  "Content-Type: text/plain; charset=\"utf-8\"\r\n"
+  "Content-Transfer-Encoding: 8bit\r\n"
+  "\r\n"
+  "Plaintext section.\r\n"
+  "\r\n"
+  "--ABCDEF\r\n"
+  "Content-Type: text/html; charset=\"utf-8\"\r\n"
+  "Content-Transfer-Encoding: 8bit\r\n"
+  "\r\n"
+  "<html>\n"
+  " <head><title>HTML/Plaintext Email</title></head>\n"
+  " <body>\n"
+  "  <h1>HTML section</h1>\n"
+  "  <h2>Heading 2</h2>\n"
+  " </body>\n"
+  "</html>\n"
+  "...\n"
+  "..\n"
+  ".\n"
+  ".";
+
+  rc = smtp_open(config->server,
+                 config->port,
+                 SMTP_TEST_DEFAULT_CONNECTION_SECURITY,
+                 SMTP_TEST_DEFAULT_FLAGS,
+                 SMTP_TEST_DEFAULT_CAFILE,
+                 &config->smtp);
+  assert(rc == SMTP_STATUS_OK);
+
+  smtp_header_clear_all(config->smtp);
+
+  rc = smtp_header_add(config->smtp,
+                       "Subject",
+                       "SMTP Test: HTML Email (with plaintext)");
+  assert(rc == SMTP_STATUS_OK);
+
+  rc = smtp_header_add(config->smtp,
+                       "Content-Type",
+                       "multipart/alternative; boundary=\"ABCDEF\"");
+  assert(rc == SMTP_STATUS_OK);
+
+  rc = smtp_address_add(config->smtp,
+                        SMTP_ADDRESS_FROM,
+                        config->email_from,
+                        SMTP_TEST_DEFAULT_FROM_NAME);
+  assert(rc == SMTP_STATUS_OK);
+
+  rc = smtp_address_add(config->smtp,
+                        SMTP_ADDRESS_TO,
+                        config->email_to,
+                        SMTP_TEST_DEFAULT_TO_NAME);
+  assert(rc == SMTP_STATUS_OK);
+
+  rc = smtp_mail(config->smtp, html_body);
+  assert(rc == SMTP_STATUS_OK);
+
+  rc = smtp_close(config->smtp);
+  assert(rc == SMTP_STATUS_OK);
+}
+
+/**
+ * Send HTML emails, overriding the Content-Type.
+ *
+ * @param[in] config SMTP server context.
+ */
+static void
+smtp_func_test_all_html(struct smtp_test_config *const config){
+  smtp_func_test_html(config);
+  smtp_func_test_html_with_plaintext(config);
+}
+
+/**
  * Test failure or error conditions not covered by any of the other failure
  * tests.
  *
@@ -4882,6 +5045,7 @@ smtp_func_test_postfix(void){
   smtp_func_test_all_body(&config);
   smtp_func_test_all_write(&config);
   smtp_func_test_all_nodebug(&config);
+  smtp_func_test_all_html(&config);
 }