diff --git a/client/client_test.go b/client/client_test.go
index a6784ff8a..dbcf0978c 100644
--- a/client/client_test.go
+++ b/client/client_test.go
@@ -5,8 +5,10 @@ import (
 	"github.com/stretchr/testify/require"
 	"heckel.io/ntfy/v2/client"
 	"heckel.io/ntfy/v2/log"
+	"heckel.io/ntfy/v2/server"
 	"heckel.io/ntfy/v2/test"
 	"os"
+	"strings"
 	"testing"
 	"time"
 )
@@ -101,6 +103,24 @@ func TestClient_Publish_Poll(t *testing.T) {
 	require.Equal(t, "some delayed message", messages[1].Message)
 }
 
+func TestClient_Publish_HeaderWithNewlines(t *testing.T) {
+	conf := server.NewConfig()
+	conf.BaseURL = "http://127.0.0.1" // Attachments require a base URL
+	s, port := test.StartServerWithConfig(t, conf)
+	defer test.StopServer(t, s, port)
+	c := client.New(newTestConfig(port))
+
+	// With an attachment as the body, message and title must travel as headers (see #1808)
+	msg, err := c.PublishReader("mytopic", strings.NewReader("file contents"),
+		client.WithFilename("test.txt"),
+		client.WithMessage("message\n  with\n  newlines"),
+		client.WithTitle("title\nwith newline"))
+	require.Nil(t, err)
+	require.Equal(t, "message\n  with\n  newlines", msg.Message)
+	require.Equal(t, "title\nwith newline", msg.Title)
+	require.Equal(t, "test.txt", msg.Attachment.Name)
+}
+
 func newTestConfig(port int) *client.Config {
 	c := client.NewConfig()
 	c.DefaultHost = fmt.Sprintf("http://127.0.0.1:%d", port)
diff --git a/client/options.go b/client/options.go
index b99f16731..6c5950f67 100644
--- a/client/options.go
+++ b/client/options.go
@@ -3,6 +3,7 @@ package client
 import (
 	"fmt"
 	"heckel.io/ntfy/v2/util"
+	"mime"
 	"net/http"
 	"strings"
 	"time"
@@ -182,11 +183,12 @@ func WithTagsFilter(tags []string) SubscribeOption {
 	return WithQueryParam("tags", strings.Join(tags, ","))
 }
 
-// WithHeader is a generic option to add headers to a request
+// WithHeader is a generic option to add headers to a request. Values with characters that are not
+// allowed in HTTP headers (e.g. newlines) are RFC 2047 encoded, which the server decodes.
 func WithHeader(header, value string) RequestOption {
 	return func(r *http.Request) error {
 		if value != "" {
-			r.Header.Set(header, value)
+			r.Header.Set(header, mime.BEncoding.Encode("utf-8", value))
 		}
 		return nil
 	}
diff --git a/server/server.go b/server/server.go
index 4e7997bab..286c3ee38 100644
--- a/server/server.go
+++ b/server/server.go
@@ -1405,7 +1405,7 @@ func (s *Server) parsePublishParams(r *http.Request, m *model.Message) (cache bo
 		}
 	}
 	contentType, markdown := readParam(r, "content-type", "content_type"), readBoolParam(r, false, "x-markdown", "markdown", "md")
-	if markdown || strings.ToLower(contentType) == "text/markdown" {
+	if markdown || isMarkdownContentType(contentType) {
 		m.ContentType = "text/markdown"
 	}
 	unifiedpush = readBoolParam(r, false, "x-unifiedpush", "unifiedpush", "up") // see GET too!
diff --git a/server/server_test.go b/server/server_test.go
index b5eb89dba..3f27bfd00 100644
--- a/server/server_test.go
+++ b/server/server_test.go
@@ -2231,6 +2231,48 @@ func TestServer_PublishMarkdown_NotMarkdown(t *testing.T) {
 	})
 }
 
+func TestServer_PublishMarkdown_ContentTypeParameters(t *testing.T) {
+	tests := []struct {
+		contentType string
+		expected    string
+	}{
+		{"text/markdown; charset=utf-8", "text/markdown"},
+		{"TEXT/MARKDOWN", "text/markdown"},
+		{"text/markdown;charset=UTF-8", "text/markdown"},
+		{"TEXT/Markdown ; charset=utf-8", "text/markdown"},
+		{"text/markdown; variant=GFM", "text/markdown"},
+		{"text/markdownx; charset=utf-8", ""},
+		{"text/plain; charset=utf-8", ""},
+		{"text/markdown; charset=\"unterminated", ""},
+	}
+	forEachBackend(t, func(t *testing.T, databaseURL string) {
+		for _, tc := range tests {
+			t.Run(tc.contentType, func(t *testing.T) {
+				s := newTestServer(t, newTestConfig(t, databaseURL))
+				response := request(t, s, "PUT", "/mytopic", "**make this bold**", map[string]string{
+					"Content-Type": tc.contentType,
+				})
+				require.Equal(t, 200, response.Code)
+
+				m := toMessage(t, response.Body.String())
+				require.Equal(t, "**make this bold**", m.Message)
+				require.Equal(t, tc.expected, m.ContentType)
+			})
+		}
+	})
+}
+
+func TestServer_PublishMarkdown_ContentTypeQueryParamWithCharset(t *testing.T) {
+	forEachBackend(t, func(t *testing.T, databaseURL string) {
+		s := newTestServer(t, newTestConfig(t, databaseURL))
+		response := request(t, s, "PUT", "/mytopic?content-type=text/markdown%3B%20charset=utf-8", "**make this bold**", nil)
+		require.Equal(t, 200, response.Code)
+
+		m := toMessage(t, response.Body.String())
+		require.Equal(t, "text/markdown", m.ContentType)
+	})
+}
+
 func TestServer_PublishAsJSON(t *testing.T) {
 	forEachBackend(t, func(t *testing.T, databaseURL string) {
 		s := newTestServer(t, newTestConfig(t, databaseURL))
diff --git a/server/util.go b/server/util.go
index 305f63eaa..33df051ae 100644
--- a/server/util.go
+++ b/server/util.go
@@ -196,3 +196,13 @@ func maybeIgnoreSpecialHeader(name, value string) string {
 	}
 	return value
 }
+
+// isMarkdownContentType returns true if the given Content-Type header value is "text/markdown",
+// ignoring case and any media type parameters, e.g. "text/markdown; charset=utf-8".
+func isMarkdownContentType(contentType string) bool {
+	mediaType, _, err := mime.ParseMediaType(contentType)
+	if err != nil {
+		return strings.ToLower(contentType) == "text/markdown"
+	}
+	return strings.ToLower(mediaType) == "text/markdown"
+}