diff --git a/Cargo.toml b/Cargo.toml
index 17bb206..2caed3c 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -11,7 +11,7 @@ codegen-units = 1
 [dependencies]
 email = "*"
 email-encoding = "*"
-lettre = {version="*", features=["builder"]}
+quoted_printable = "*"
 charset = "*"
 mailparse = "*"
 mediatype = "*"
diff --git a/src/body.rs b/src/body.rs
new file mode 100644
index 0000000..c77a8b1
--- /dev/null
+++ b/src/body.rs
@@ -0,0 +1,136 @@
+//! Body transfer-encoding.
+
+use std::fmt::{self, Display};
+use std::mem;
+
+use email_encoding::body::{Encoding, base64};
+
+/// The `Content-Transfer-Encoding` of a body, as defined in RFC 2045 section 6.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum ContentTransferEncoding {
+    SevenBit,
+    EightBit,
+    QuotedPrintable,
+    Base64,
+    Binary,
+}
+
+impl Display for ContentTransferEncoding {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str(match self {
+            Self::SevenBit => "7bit",
+            Self::EightBit => "8bit",
+            Self::QuotedPrintable => "quoted-printable",
+            Self::Base64 => "base64",
+            Self::Binary => "binary",
+        })
+    }
+}
+
+/// Body content to be encoded.
+///
+/// Pass [`BodyContent::Text`] whenever the content is valid UTF-8: it allows the more
+/// efficient `7bit` and `quoted-printable` encodings to be chosen, while binary content
+/// always ends up as `base64`.
+#[derive(Debug, Clone)]
+pub enum BodyContent {
+    Text(String),
+    Binary(Vec<u8>),
+}
+
+impl From<String> for BodyContent {
+    fn from(content: String) -> Self {
+        Self::Text(content)
+    }
+}
+
+impl From<&str> for BodyContent {
+    fn from(content: &str) -> Self {
+        Self::Text(content.to_owned())
+    }
+}
+
+impl From<Vec<u8>> for BodyContent {
+    fn from(content: Vec<u8>) -> Self {
+        Self::Binary(content)
+    }
+}
+
+impl From<&[u8]> for BodyContent {
+    fn from(content: &[u8]) -> Self {
+        Self::Binary(content.to_vec())
+    }
+}
+
+impl From<BodyContent> for Vec<u8> {
+    fn from(content: BodyContent) -> Self {
+        match content {
+            BodyContent::Text(content) => content.into_bytes(),
+            BodyContent::Binary(content) => content,
+        }
+    }
+}
+
+/// Encode `content`, choosing the most compact of `7bit`, `quoted-printable` and `base64`.
+///
+/// Line endings of text content are normalized to CRLF.
+pub fn encode(content: impl Into<BodyContent>) -> (Vec<u8>, ContentTransferEncoding) {
+    let mut content = content.into();
+
+    // Chosen before normalizing line endings, since inserting `\r` changes line lengths.
+    let encoding = match &content {
+        BodyContent::Text(content) => Encoding::choose(content.as_str(), false),
+        BodyContent::Binary(content) => Encoding::choose(content.as_slice(), false),
+    };
+
+    if let BodyContent::Text(content) = &mut content {
+        crlf_line_endings(content);
+    }
+    let content = Vec::from(content);
+
+    match encoding {
+        Encoding::SevenBit => (content, ContentTransferEncoding::SevenBit),
+        Encoding::EightBit => (content, ContentTransferEncoding::EightBit),
+        Encoding::QuotedPrintable => (
+            quoted_printable::encode(content),
+            ContentTransferEncoding::QuotedPrintable,
+        ),
+        Encoding::Base64 => {
+            let mut encoded = String::with_capacity(base64::encoded_len(content.len()));
+            base64::encode(&content, &mut encoded).expect("String is always writable");
+            (encoded.into_bytes(), ContentTransferEncoding::Base64)
+        }
+    }
+}
+
+/// In place conversion to CRLF line endings.
+///
+/// Ported from `lettre::message::body` (MIT licensed).
+fn crlf_line_endings(content: &mut String) {
+    // relies on the indices being in reverse order
+    for ix in lone_lf_indices(content) {
+        content.insert(ix, '\r');
+    }
+}
+
+/// Find, in reverse order, the indices at which a `\r` has to be inserted to give
+/// `content` CRLF line endings.
+fn lone_lf_indices(content: &str) -> Vec<usize> {
+    let mut indices = Vec::new();
+
+    let mut found_lf = false;
+    for (ix, c) in content.char_indices().rev() {
+        if mem::take(&mut found_lf) && c != '\r' {
+            // the previous character was a `\n`, but this one is not a `\r`
+            indices.push(ix + c.len_utf8());
+        }
+        found_lf = c == '\n';
+    }
+
+    if found_lf {
+        // the first character is a `\n`
+        indices.push(0);
+    }
+
+    indices
+}
diff --git a/src/lib.rs b/src/lib.rs
index 22e2bdd..169a9cb 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,15 +1,15 @@
 #![forbid(unsafe_code)]
 
+pub mod body;
 pub mod header;
 
 #[cfg(test)]
 mod tests;
 
+pub use body::{BodyContent, ContentTransferEncoding};
 use header::CowHeader;
 pub use header::{Header, HeaderMap, parse_headers};
 
-use lettre::message::MaybeString;
-use lettre::message::header::ContentTransferEncoding;
 use mailparse::{
     DispositionType, MailParseError, ParsedContentDisposition, ParsedContentType, body::Body,
     parse_content_disposition, parse_content_type,
@@ -268,29 +268,27 @@ impl<'a, H: Header<'a> + 'a> CowMail<'a, H> {
 
         self.headers.add_header("Content-Type", ctype);
 
-        let body = lettre::message::Body::new(content);
-        let encoding = body.encoding();
+        let (bytes, encoding) = body::encode(content);
         if encoding != ContentTransferEncoding::SevenBit {
             self.headers.add_header("Content-Transfer-Encoding", encoding);
         }
 
-        self.body_bytes = Cow::Owned(body.into_vec());
+        self.body_bytes = Cow::Owned(bytes);
     }
 
-    pub fn set_content_raw<B: Into<MaybeString>>(&mut self, content: B, ctype: Option<MediaType>) {
+    pub fn set_content_raw<B: Into<BodyContent>>(&mut self, content: B, ctype: Option<MediaType>) {
         self.clear_content();
-        let body = lettre::message::Body::new(content);
 
         if let Some(ctype) = ctype {
             self.headers.add_header("Content-Type", ctype);
         }
 
-        let encoding = body.encoding();
+        let (bytes, encoding) = body::encode(content);
         if encoding != ContentTransferEncoding::SevenBit {
             self.headers.add_header("Content-Transfer-Encoding", encoding);
         }
 
-        self.body_bytes = Cow::Owned(body.into_vec());
+        self.body_bytes = Cow::Owned(bytes);
     }
 
     pub fn get_filename(&self) -> Option<String> {