diff --git a/lib/easy.c b/lib/easy.c
index 398b20edd1..8f32698b93 100644
--- a/lib/easy.c
+++ b/lib/easy.c
@@ -891,7 +891,7 @@ static CURLcode dupset(struct Curl_easy *dst, struct Curl_easy *src)
   /* Copy src->set into dst->set first, then deal with the strings
      afterwards */
   dst->set = src->set;
-  Curl_mime_initpart(&dst->set.mimepost);
+  dst->set.mimepostp = NULL;
 
   /* clear all dest string and blob pointers first, in case we error out
      mid-function */
@@ -927,8 +927,17 @@ static CURLcode dupset(struct Curl_easy *dst, struct Curl_easy *src)
     dst->set.postfields = dst->set.str[i];
   }
 
-  /* Duplicate mime data. */
-  result = Curl_mime_duppart(dst, &dst->set.mimepost, &src->set.mimepost);
+  if(src->set.mimepostp) {
+    /* Duplicate mime data. Get a mimepost struct for the clone as well */
+    dst->set.mimepostp = curlx_malloc(sizeof(*dst->set.mimepostp));
+    if(!dst->set.mimepostp)
+      return CURLE_OUT_OF_MEMORY;
+
+    Curl_mime_initpart(dst->set.mimepostp);
+    result = Curl_mime_duppart(dst, dst->set.mimepostp, src->set.mimepostp);
+    if(result)
+      return result;
+  }
 
   if(src->set.resolve)
     dst->state.resolve = dst->set.resolve;
diff --git a/lib/http.c b/lib/http.c
index 0343aba3e7..f452fe2550 100644
--- a/lib/http.c
+++ b/lib/http.c
@@ -2117,7 +2117,7 @@ static CURLcode set_post_reader(struct Curl_easy *data, Curl_HttpReq httpreq)
   switch(httpreq) {
 #ifndef CURL_DISABLE_MIME
   case HTTPREQ_POST_MIME:
-    data->state.mimepost = &data->set.mimepost;
+    data->state.mimepost = data->set.mimepostp;
     break;
 #endif
 #ifndef CURL_DISABLE_FORM_API
diff --git a/lib/imap.c b/lib/imap.c
index 0af18780d4..8fe87d9932 100644
--- a/lib/imap.c
+++ b/lib/imap.c
@@ -859,22 +859,23 @@ static CURLcode imap_perform_append(struct Curl_easy *data,
 
 #ifndef CURL_DISABLE_MIME
   /* Prepare the mime data if some. */
-  if(data->set.mimepost.kind != MIMEKIND_NONE) {
+  if(IS_MIME_POST(data)) {
+    curl_mimepart *postp = data->set.mimepostp;
     /* Use the whole structure as data. */
-    data->set.mimepost.flags &= ~(unsigned int)MIME_BODY_ONLY;
+    postp->flags &= ~(unsigned int)MIME_BODY_ONLY;
 
     /* Add external headers and mime version. */
-    curl_mime_headers(&data->set.mimepost, data->set.headers, 0);
-    result = Curl_mime_prepare_headers(data, &data->set.mimepost, NULL,
+    curl_mime_headers(postp, data->set.headers, 0);
+    result = Curl_mime_prepare_headers(data, postp, NULL,
                                        NULL, MIMESTRATEGY_MAIL);
 
     if(!result)
       if(!Curl_checkheaders(data, STRCONST("Mime-Version")))
-        result = Curl_mime_add_header(&data->set.mimepost.curlheaders,
+        result = Curl_mime_add_header(&postp->curlheaders,
                                       "Mime-Version: 1.0");
 
     if(!result)
-      result = Curl_creader_set_mime(data, &data->set.mimepost);
+      result = Curl_creader_set_mime(data, postp);
     if(result)
       return result;
     data->state.infilesize = Curl_creader_client_length(data);
diff --git a/lib/setopt.c b/lib/setopt.c
index 5ea3cbbb9b..44fcde6fe6 100644
--- a/lib/setopt.c
+++ b/lib/setopt.c
@@ -1383,6 +1383,38 @@ static CURLcode setopt_slist(struct Curl_easy *data, CURLoption option,
   return result;
 }
 
+#if !defined(CURL_DISABLE_HTTP) || !defined(CURL_DISABLE_SMTP) ||       \
+  !defined(CURL_DISABLE_IMAP)
+# ifndef CURL_DISABLE_MIME
+static CURLcode setopt_mimepost(struct Curl_easy *data, curl_mime *mimep)
+{
+  /*
+   * Set to make us do MIME POST
+   */
+  CURLcode result;
+  struct UserDefined *s = &data->set;
+  if(!s->mimepostp) {
+    s->mimepostp = curlx_malloc(sizeof(*s->mimepostp));
+    if(!s->mimepostp)
+      return CURLE_OUT_OF_MEMORY;
+    Curl_mime_initpart(s->mimepostp);
+  }
+
+  result = Curl_mime_set_subparts(s->mimepostp, mimep, FALSE);
+  if(!result) {
+    s->method = HTTPREQ_POST_MIME;
+    s->opt_no_body = FALSE; /* this is implied */
+#ifndef CURL_DISABLE_FORM_API
+    Curl_mime_cleanpart(data->state.formp);
+    Curl_safefree(data->state.formp);
+    data->state.mimepost = NULL;
+#endif
+  }
+  return result;
+}
+#endif /* !CURL_DISABLE_MIME */
+#endif /* !CURL_DISABLE_HTTP || !CURL_DISABLE_SMTP || !CURL_DISABLE_IMAP */
+
 /* assorted pointer type arguments */
 static CURLcode setopt_pointers(struct Curl_easy *data, CURLoption option,
                                 va_list param)
@@ -1405,25 +1437,11 @@ static CURLcode setopt_pointers(struct Curl_easy *data, CURLoption option,
     break;
 #endif /* !CURL_DISABLE_FORM_API */
 #endif /* !CURL_DISABLE_HTTP */
-#if !defined(CURL_DISABLE_HTTP) || !defined(CURL_DISABLE_SMTP) || \
+#if !defined(CURL_DISABLE_HTTP) || !defined(CURL_DISABLE_SMTP) ||       \
   !defined(CURL_DISABLE_IMAP)
 # ifndef CURL_DISABLE_MIME
   case CURLOPT_MIMEPOST:
-    /*
-     * Set to make us do MIME POST
-     */
-    result = Curl_mime_set_subparts(&s->mimepost,
-                                    va_arg(param, curl_mime *),
-                                    FALSE);
-    if(!result) {
-      s->method = HTTPREQ_POST_MIME;
-      s->opt_no_body = FALSE; /* this is implied */
-#ifndef CURL_DISABLE_FORM_API
-      Curl_mime_cleanpart(data->state.formp);
-      Curl_safefree(data->state.formp);
-      data->state.mimepost = NULL;
-#endif
-    }
+    result = setopt_mimepost(data, va_arg(param, curl_mime *));
     break;
 #endif /* !CURL_DISABLE_MIME */
 #endif /* !CURL_DISABLE_HTTP || !CURL_DISABLE_SMTP || !CURL_DISABLE_IMAP */
diff --git a/lib/smtp.c b/lib/smtp.c
index 471c823152..f3f3fe52d5 100644
--- a/lib/smtp.c
+++ b/lib/smtp.c
@@ -766,22 +766,24 @@ static CURLcode smtp_perform_mail(struct Curl_easy *data,
 
 #ifndef CURL_DISABLE_MIME
   /* Prepare the mime data if some. */
-  if(data->set.mimepost.kind != MIMEKIND_NONE) {
+  if(IS_MIME_POST(data)) {
+    curl_mimepart *postp = data->set.mimepostp;
+
     /* Use the whole structure as data. */
-    data->set.mimepost.flags &= ~(unsigned int)MIME_BODY_ONLY;
+    postp->flags &= ~(unsigned int)MIME_BODY_ONLY;
 
     /* Add external headers and mime version. */
-    curl_mime_headers(&data->set.mimepost, data->set.headers, 0);
-    result = Curl_mime_prepare_headers(data, &data->set.mimepost, NULL,
+    curl_mime_headers(postp, data->set.headers, 0);
+    result = Curl_mime_prepare_headers(data, postp, NULL,
                                        NULL, MIMESTRATEGY_MAIL);
 
     if(!result)
       if(!Curl_checkheaders(data, STRCONST("Mime-Version")))
-        result = Curl_mime_add_header(&data->set.mimepost.curlheaders,
+        result = Curl_mime_add_header(&postp->curlheaders,
                                       "Mime-Version: 1.0");
 
     if(!result)
-      result = Curl_creader_set_mime(data, &data->set.mimepost);
+      result = Curl_creader_set_mime(data, postp);
     if(result)
       goto out;
     data->state.infilesize = Curl_creader_total_length(data);
diff --git a/lib/url.c b/lib/url.c
index 130be1952c..47df6b3913 100644
--- a/lib/url.c
+++ b/lib/url.c
@@ -175,7 +175,8 @@ void Curl_freeset(struct Curl_easy *data)
   Curl_bufref_free(&data->state.referer);
   Curl_bufref_free(&data->state.url);
 
-  Curl_mime_cleanpart(&data->set.mimepost);
+  Curl_mime_cleanpart(data->set.mimepostp);
+  Curl_safefree(data->set.mimepostp);
 
 #ifndef CURL_DISABLE_COOKIES
   curl_slist_free_all(data->state.cookielist);
@@ -385,8 +386,6 @@ void Curl_init_userdefined(struct Curl_easy *data)
   set->socks5auth = CURLAUTH_BASIC | CURLAUTH_GSSAPI;
 #endif
 
-  Curl_mime_initpart(&set->mimepost);
-
   Curl_ssl_easy_config_init(data);
 #ifndef CURL_DISABLE_DOH
   set->doh_verifyhost = TRUE;
diff --git a/lib/urldata.h b/lib/urldata.h
index 0517b9b2d0..a41e1e62dd 100644
--- a/lib/urldata.h
+++ b/lib/urldata.h
@@ -1341,7 +1341,7 @@ struct UserDefined {
   struct curl_slist *headers; /* linked list of extra headers */
   struct curl_httppost *httppost;  /* linked list of old POST data */
 #if !defined(CURL_DISABLE_MIME) || !defined(CURL_DISABLE_FORM_API)
-  curl_mimepart mimepost;  /* MIME/POST data. */
+  curl_mimepart *mimepostp;  /* MIME/POST data. */
 #endif
 #ifndef CURL_DISABLE_TELNET
   struct curl_slist *telnet_options; /* linked list of telnet options */
@@ -1591,7 +1591,8 @@ struct UserDefined {
 };
 
 #ifndef CURL_DISABLE_MIME
-#define IS_MIME_POST(a) ((a)->set.mimepost.kind != MIMEKIND_NONE)
+#define IS_MIME_POST(a)                                                 \
+  ((a)->set.mimepostp && ((a)->set.mimepostp->kind != MIMEKIND_NONE))
 #else
 #define IS_MIME_POST(a) FALSE
 #endif
diff --git a/tests/libtest/lib589.c b/tests/libtest/lib589.c
index b8d9e2350d..cf85652378 100644
--- a/tests/libtest/lib589.c
+++ b/tests/libtest/lib589.c
@@ -27,6 +27,8 @@ static CURLcode test_lib589(const char *URL)
 {
   CURL *curl;
   CURLcode result = CURLE_OK;
+  curl_mime *mime = NULL;
+  curl_mimepart *part;
 
   if(curl_global_init(CURL_GLOBAL_ALL) != CURLE_OK) {
     curl_mfprintf(stderr, "curl_global_init() failed\n");
@@ -46,13 +48,14 @@ static CURLcode test_lib589(const char *URL)
   test_setopt(curl, CURLOPT_HEADER, 1L); /* include header */
 
   if(testnum == 584) {
-    curl_mime *mime = curl_mime_init(curl);
-    curl_mimepart *part = curl_mime_addpart(mime);
-    curl_mime_name(part, "fake");
-    curl_mime_data(part, "party", 5);
-    test_setopt(curl, CURLOPT_MIMEPOST, mime);
-    result = curl_easy_perform(curl);
-    curl_mime_free(mime);
+    mime = curl_mime_init(curl);
+    part = curl_mime_addpart(mime);
+    if(mime && part) {
+      curl_mime_name(part, "fake");
+      curl_mime_data(part, "party", 5);
+      test_setopt(curl, CURLOPT_MIMEPOST, mime);
+      result = curl_easy_perform(curl);
+    }
     if(result)
       goto test_cleanup;
   }
@@ -65,6 +68,7 @@ static CURLcode test_lib589(const char *URL)
 test_cleanup:
 
   /* always cleanup */
+  curl_mime_free(mime);
   curl_easy_cleanup(curl);
   curl_global_cleanup();
 
diff --git a/tests/unit/unit3214.c b/tests/unit/unit3214.c
index ae03d5410c..6b10352953 100644
--- a/tests/unit/unit3214.c
+++ b/tests/unit/unit3214.c
@@ -41,7 +41,7 @@ static void checksize(const char *name, size_t size, size_t allowed)
 }
 
 /* the maximum sizes we allow specific structs to grow to */
-#define MAX_CURL_EASY           5850
+#define MAX_CURL_EASY           5370
 #define MAX_CONNECTDATA         1300
 #define MAX_CURL_MULTI          850
 #define MAX_CURL_HTTPPOST       112