diff --git a/message_cache.cc b/message_cache.cc
new file mode 100644
index 0000000..34187b4
--- /dev/null
+++ b/message_cache.cc
@@ -0,0 +1,246 @@
+#include "message_cache.hh"
+
+pEp::MessageCache message_cache;
+
+namespace pEp {
+    DYNAMIC_API PEP_STATUS MessageCache::cache_decrypt_message(
+            PEP_SESSION session,
+            message *src,
+            message **dst,
+            stringlist_t **keylist,
+            PEP_rating *rating,
+            PEP_decrypt_flags_t *flags
+    )
+    {
+        return message_cache.decrypt_message(session, src, dst, keylist,
+                rating, flags);
+    }
+
+    DYNAMIC_API PEP_STATUS MessageCache::cached_mime_encode_message(
+            which one,
+            const message * msg,
+            bool omit_fields,
+            char **mimetext,
+            bool has_pEp_msg_attachment     
+        )
+    {
+        return message_cache.mime_encode_message(one, msg, omit_fields,
+                mimetext, has_pEp_msg_attachment);
+    }
+
+    static char *dup(const char *src)
+    {
+        if (!src)
+            return nullptr;
+
+        char * dst = ::strdup(src);
+        assert(dst);
+        if (!dst)
+            throw std::bad_alloc();
+
+        return dst;
+    }
+
+    static timestamp *dup(const ::timestamp *src)
+    {
+        if (!src)
+            return nullptr;
+
+        ::timestamp * dst = ::timestamp_dup(src);
+        if (!dst)
+            throw std::bad_alloc();
+
+        return dst;
+    }
+
+    static ::pEp_identity *dup(const ::pEp_identity *src)
+    {
+        if (!src)
+            return nullptr;
+
+        ::pEp_identity * dst = ::identity_dup(src);
+        if (!dst)
+            throw std::bad_alloc();
+
+        return dst;
+    }
+
+    static identity_list *dup(const ::identity_list *src)
+    {
+        if (!src)
+            return nullptr;
+
+        ::identity_list * dst = ::identity_list_dup(src);
+        if (!dst)
+            throw std::bad_alloc();
+
+        return dst;
+    }
+
+    static stringlist_t *dup(const ::stringlist_t *src)
+    {
+        if (!src)
+            return nullptr;
+
+        ::stringlist_t * dst = ::stringlist_dup(src);
+        if (!dst)
+            throw std::bad_alloc();
+
+        return dst;
+    }
+
+    static stringpair_list_t *dup(const ::stringpair_list_t *src)
+    {
+        if (!src)
+            return nullptr;
+
+        ::stringpair_list_t * dst = ::stringpair_list_dup(src);
+        if (!dst)
+            throw std::bad_alloc();
+
+        return dst;
+    }
+
+    static ::message_ref_list *dup(const ::message_ref_list *src) {
+        if (!src)
+            return nullptr;
+
+        ::message_ref_list *dst = (::message_ref_list *) ::calloc(1,
+                sizeof(::message_ref_list));
+        assert(dst);
+        if (!dst)
+            throw std::bad_alloc();
+
+        ::message_ref_list *d = dst;
+        for (const message_ref_list *s = src; s; s = s->next) {
+            d->msg_ref = s->msg_ref;
+            if (s->next) {
+                d->next = (::message_ref_list *) ::calloc(1,
+                        sizeof(::message_ref_list));
+                assert(d);
+                if (!d)
+                    throw std::bad_alloc();
+                d = d->next;
+            }
+        }
+
+        return dst;
+    }
+
+    static bool emptystr(const char *str)
+    {
+        if (!(str && str[0]))
+            return true;
+        return false;
+    }
+
+    ::message *MessageCache::empty_message_copy(::message *src)
+    {
+        if (!src)
+            return nullptr;
+
+        ::message *dst = ::new_message(src->dir);
+        if (!dst)
+            throw std::bad_alloc();
+
+        dst->id = dup(src->id);
+        dst->shortmsg = dup(src->shortmsg);
+
+        if (!emptystr(src->longmsg))
+            dst->longmsg = dup("pEp");
+
+        if (!emptystr(src->longmsg_formatted))
+            dst->longmsg_formatted = dup("<pEp/>");
+        
+        // attachments are never copied
+
+        dst->rawmsg_ref = src->rawmsg_ref;
+        dst->rawmsg_size = src->rawmsg_size;
+
+        dst->sent = dup(src->sent);
+        dst->recv = dup(src->recv);
+
+        dst->from = dup(src->from);
+        dst->to = dup(src->to);
+        dst->cc = dup(src->cc);
+        dst->bcc = dup(src->bcc);
+
+        dst->reply_to = dup(src->reply_to);
+        dst->in_reply_to = dup(src->in_reply_to);
+
+        dst->refering_msg_ref = src->refering_msg_ref;
+        dst->references = dup(src->references);
+        dst->refered_by = dup(src->refered_by);
+
+        dst->keywords = dup(src->keywords);
+        dst->comments = dup(src->comments);
+        dst->opt_fields = dup(src->opt_fields);
+        dst->enc_format = src->enc_format;
+        dst->_sender_fpr = dup(src->_sender_fpr);
+
+        return dst;
+    }
+
+    DYNAMIC_API PEP_STATUS MessageCache::decrypt_message(
+            PEP_SESSION session,
+            message *src,
+            message **dst,
+            stringlist_t **keylist,
+            PEP_rating *rating,
+            PEP_decrypt_flags_t *flags
+    )
+    {
+        if (!src || emptystr(src->id))
+            return PEP_ILLEGAL_VALUE;
+
+        PEP_STATUS status = ::decrypt_message(session, src, dst, keylist,
+                rating, flags);
+
+        ::message *_cpy = empty_message_copy(src);
+
+        ::message *_src;
+        ::memcpy(_src, src, sizeof(::message));
+        ::memcpy(src, _cpy, sizeof(::message));
+
+        ::message *_dst = *dst;
+        *dst = empty_message_copy(_dst);
+
+        message_cache._cache.emplace(std::make_pair(std::string(_src->id),
+                    cache_entry(_src, _dst)));
+        return status;
+    }
+
+    DYNAMIC_API PEP_STATUS MessageCache::mime_encode_message(
+            which one,
+            const message * msg,
+            bool omit_fields,
+            char **mimetext,
+            bool has_pEp_msg_attachment     
+        )
+    {
+        if (!msg || emptystr(msg->id))
+            return PEP_ILLEGAL_VALUE;
+
+        if (one != msg_src && one != msg_dst)
+            return PEP_ILLEGAL_VALUE;
+
+        ::message *_msg;
+        if (one == msg_src) {
+            _msg = _cache.at(std::string(msg->id)).src;
+            ::free_message(_cache.at(msg->id).dst);
+        }
+        else /* msg_dst */ {
+            _msg = _cache.at(std::string(msg->id)).dst;
+            ::free_message(_cache.at(msg->id).src);
+        }
+
+        PEP_STATUS status = ::mime_encode_message(_msg, omit_fields, mimetext,
+                has_pEp_msg_attachment);
+
+        ::free_message(_msg);
+        _cache.erase(msg->id);
+
+        return status;
+    }
+};
+
diff --git a/message_cache.hh b/message_cache.hh
new file mode 100644
index 0000000..0502d60
--- /dev/null
+++ b/message_cache.hh
@@ -0,0 +1,73 @@
+#pragma once
+
+#include <string>
+#include <unordered_map>
+#include <mutex>
+#include <pEp/message_api.h>
+#include <pEp/mime.h>
+
+namespace pEp {
+    class MessageCache {
+        struct cache_entry {
+            cache_entry(::message *s, ::message *d)
+                : src(s), dst(d) { }
+            ~cache_entry() {
+                ::free_message(src);
+                ::free_message(dst);
+            };
+
+            ::message *src;
+            ::message *dst;
+        };
+
+        using cache = std::unordered_map<std::string, cache_entry>;
+
+        cache _cache;
+        std::mutex _mtx;
+
+    public:
+        static 
+        DYNAMIC_API PEP_STATUS cache_decrypt_message(
+                PEP_SESSION session,
+                message *src,
+                message **dst,
+                stringlist_t **keylist,
+                PEP_rating *rating,
+                PEP_decrypt_flags_t *flags
+        );
+
+        enum which { msg_src, msg_dst };;
+
+        static
+        DYNAMIC_API PEP_STATUS cached_mime_encode_message(
+                which one,
+                const message * msg,
+                bool omit_fields,
+                char **mimetext,
+                bool has_pEp_msg_attachment     
+            );
+
+    protected:
+        DYNAMIC_API PEP_STATUS decrypt_message(
+                PEP_SESSION session,
+                message *src,
+                message **dst,
+                stringlist_t **keylist,
+                PEP_rating *rating,
+                PEP_decrypt_flags_t *flags
+        );
+
+        DYNAMIC_API PEP_STATUS mime_encode_message(
+                which one,
+                const message * src,
+                bool omit_fields,
+                char **mimetext,
+                bool has_pEp_msg_attachment
+            );
+
+        static ::message *empty_message_copy(::message *src);
+    };
+
+    extern MessageCache message_cache;
+};
+