diff --git a/changelogs/unreleased/enable-smtp.md b/changelogs/unreleased/enable-smtp.md
new file mode 100755
index 0000000000000000000000000000000000000000..aa299b3c240f6ae237dc2ba35781424fa5daa7ca
--- /dev/null
+++ b/changelogs/unreleased/enable-smtp.md
@@ -0,0 +1,3 @@
+## feature/build
+
+* Enable smtp and smtps protocols in bundled libcurl (gh-4559).
diff --git a/cmake/BuildLibCURL.cmake b/cmake/BuildLibCURL.cmake
index 814757e101997608ba70350486a3af326e1c155d..2c62a68ba59765bc47161bd0cd2b4f6efcbc21fc 100644
--- a/cmake/BuildLibCURL.cmake
+++ b/cmake/BuildLibCURL.cmake
@@ -77,7 +77,7 @@ macro(curl_build)
 
     # Switch off the group of protocols with special flag HTTP_ONLY:
     #   ftp, file, ldap, ldaps, rtsp, dict, telnet, tftp, pop3, imap, smtp.
-    list(APPEND LIBCURL_CMAKE_FLAGS "-DHTTP_ONLY=ON")
+    list(APPEND LIBCURL_CMAKE_FLAGS "-DHTTP_ONLY=OFF")
 
     # Additionaly disable some more protocols.
     list(APPEND LIBCURL_CMAKE_FLAGS "-DCURL_DISABLE_SMB=ON")
@@ -142,7 +142,7 @@ macro(curl_build)
     list(APPEND LIBCURL_CMAKE_FLAGS "-DCURL_DISABLE_TFTP=ON")
     list(APPEND LIBCURL_CMAKE_FLAGS "-DCURL_DISABLE_POP3=ON")
     list(APPEND LIBCURL_CMAKE_FLAGS "-DCURL_DISABLE_IMAP=ON")
-    list(APPEND LIBCURL_CMAKE_FLAGS "-DCURL_DISABLE_SMTP=ON")
+    list(APPEND LIBCURL_CMAKE_FLAGS "-DCURL_DISABLE_SMTP=OFF")
 
     include(ExternalProject)
     ExternalProject_Add(
diff --git a/test/box-tap/gh-5223-curl-exports.test.lua b/test/box-tap/curl-build.test.lua
similarity index 88%
rename from test/box-tap/gh-5223-curl-exports.test.lua
rename to test/box-tap/curl-build.test.lua
index 300d60b072ee13e761a7a09a22c3653da9053af1..ae0d397b5b208cbecd19b3f8039f3e3260e0c1cc 100755
--- a/test/box-tap/gh-5223-curl-exports.test.lua
+++ b/test/box-tap/curl-build.test.lua
@@ -56,7 +56,7 @@ ffi.cdef([[
 
 local info = ffi.C.curl_version_info(7)
 local test = tap.test('curl-features')
-test:plan(3)
+test:plan(5)
 
 if test:ok(info.ssl_version ~= nil, 'Curl built with SSL support') then
     test:diag('ssl_version: ' .. ffi.string(info.ssl_version))
@@ -78,6 +78,9 @@ else
     RTLD_DEFAULT = ffi.cast("void *", 0LL)
 end
 
+--
+-- gh-5223: Check if all curl symbols are exported.
+--
 -- The following list was obtained by parsing libcurl.a static library:
 -- nm libcurl.a | grep -oP 'T \K(curl_.+)$' | sort
 local curl_symbols = {
@@ -174,4 +177,29 @@ test:test('curl_symbols', function(t)
     end
 end)
 
+local function has_protocol(protocol_str)
+    local i = 0
+    -- curl_version_info_data.protocols is a null terminated array
+    -- of pointers to char.
+    -- See curl/lib/version.c:
+    --   static const char * const protocols[]
+    local info = ffi.C.curl_version_info(7)
+    local protocol = info.protocols[i]
+    while protocol ~= nil do
+        if ffi.string(protocol) == protocol_str then
+            return true
+        end
+        i = i + 1
+        protocol = info.protocols[i]
+    end
+
+    return false
+end
+
+--
+-- gh-4559: check if smtp and smtps protocols are enabled.
+--
+test:ok(has_protocol('smtp'), 'smtp protocol is supported')
+test:ok(has_protocol('smtps'), 'smtps protocol is supported')
+
 os.exit(test:check() and 0 or 1)