diff --git a/.github/workflows/check.yml b/.github/workflows/check.yml
index 560e9e2..3ead55b 100644
--- a/.github/workflows/check.yml
+++ b/.github/workflows/check.yml
@@ -89,7 +89,7 @@ jobs:
     # https://docs.github.com/en/actions/learn-github-actions/contexts#context-availability
     strategy:
       matrix:
-        msrv: [1.56.1] # 2021 edition requires 1.56
+        msrv: [1.57.0] # base64 0.21 requires 1.57
     name: ubuntu / ${{ matrix.msrv }}
     steps:
       - uses: actions/checkout@v3
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index e165dc3..2f47488 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -122,6 +122,10 @@ jobs:
       matrix:
         os: [macos-latest, windows-latest]
     steps:
+      - run: echo "VCPKG_ROOT=$env:VCPKG_INSTALLATION_ROOT" | Out-File -FilePath $env:GITHUB_ENV -Append
+        if: runner.os == 'Windows'
+      - run: vcpkg install openssl:x64-windows-static-md
+        if: runner.os == 'Windows'
       - uses: actions/checkout@v3
         with:
           submodules: true
diff --git a/Cargo.lock b/Cargo.lock
index 2f33c09..36d9b4d 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -85,6 +85,12 @@ version = "0.13.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "904dfeac50f3cdaba28fc6f57fdcddb75f49ed61346676a78c4ffe55877802fd"
 
+[[package]]
+name = "base64"
+version = "0.21.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a4a4ddaa51a5bc52a6948f74c06d20aaaddb71924eab79b8c97a8c556e942d6a"
+
 [[package]]
 name = "bitflags"
 version = "1.3.2"
@@ -162,7 +168,7 @@ version = "0.1.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "34dd14c63662e0206599796cd5e1ad0268ab2b9d19b868d6050d688eba2bbf98"
 dependencies = [
- "base64",
+ "base64 0.13.0",
  "memchr",
 ]
 
@@ -371,7 +377,7 @@ dependencies = [
 name = "imap"
 version = "3.0.0-alpha.9"
 dependencies = [
- "base64",
+ "base64 0.21.0",
  "bufstream",
  "chrono",
  "encoding",
@@ -382,6 +388,7 @@ dependencies = [
  "mime",
  "native-tls",
  "nom",
+ "openssl",
  "ouroboros",
  "regex",
  "rustls-connector",
@@ -427,7 +434,7 @@ version = "0.10.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2eabca5e0b4d0e98e7f2243fb5b7520b6af2b65d8f87bcc86f2c75185a6ff243"
 dependencies = [
- "base64",
+ "base64 0.13.0",
  "email-encoding",
  "email_address",
  "fastrand",
@@ -791,7 +798,7 @@ version = "1.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0864aeff53f8c05aa08d86e5ef839d3dfcf07aeba2db32f12db0ef716e87bd55"
 dependencies = [
- "base64",
+ "base64 0.13.0",
 ]
 
 [[package]]
diff --git a/Cargo.toml b/Cargo.toml
index 1fb34b3..87cc351 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -26,7 +26,7 @@ regex = "1.0"
 bufstream = "0.1.3"
 imap-proto = "0.16.1"
 nom = { version = "7.1.0", default-features = false }
-base64 = "0.13"
+base64 = "0.21"
 chrono = { version = "0.4", default-features = false, features = ["std"]}
 lazy_static = "1.4"
 ouroboros = "0.15.0"
@@ -40,6 +40,7 @@ structopt = "0.3"
 encoding = "0.2.32"
 failure = "0.1.8"
 mime = "0.3.4"
+openssl = "0.10.35"
 
 [[example]]
 name = "basic"
diff --git a/src/client.rs b/src/client.rs
index f629b3e..7969497 100644
--- a/src/client.rs
+++ b/src/client.rs
@@ -1,3 +1,4 @@
+use base64::{engine::general_purpose, Engine as _};
 use bufstream::BufStream;
 use chrono::{DateTime, FixedOffset};
 use imap_proto::Response;
@@ -471,16 +472,18 @@ impl<T: Read + Write> Client<T> {
                     let data =
                         ok_or_unauth_client_err!(parse_authenticate_response(line_str), self);
                     ok_or_unauth_client_err!(
-                        base64::decode(data).map_err(|e| Error::Parse(ParseError::Authentication(
-                            data.to_string(),
-                            Some(e)
-                        ))),
+                        general_purpose::STANDARD_NO_PAD
+                            .decode(data)
+                            .map_err(|e| Error::Parse(ParseError::Authentication(
+                                data.to_string(),
+                                Some(e)
+                            ))),
                         self
                     )
                 };
 
                 let raw_response = &authenticator.process(&challenge);
-                let auth_response = base64::encode(raw_response);
+                let auth_response = general_purpose::STANDARD_NO_PAD.encode(raw_response);
                 ok_or_unauth_client_err!(
                     self.write_line(auth_response.into_bytes().as_slice()),
                     self