diff --git a/src/receive_imf/tests.rs b/src/receive_imf/tests.rs
index 1b1476313..0621bbc83 100644
--- a/src/receive_imf/tests.rs
+++ b/src/receive_imf/tests.rs
@@ -3135,6 +3135,13 @@ async fn test_thunderbird_autocrypt_unencrypted() -> Result<()> {
         .unwrap();
     assert_eq!(peerstate.prefer_encrypt, EncryptPreference::Mutual);
 
+    let raw = include_bytes!("../../test-data/message/thunderbird_encrypted.eml");
+    receive_imf(&t, raw, false).await?;
+    let peerstate = Peerstate::from_addr(&t, "alice@example.org")
+        .await?
+        .unwrap();
+    assert_eq!(peerstate.prefer_encrypt, EncryptPreference::Mutual);
+
     Ok(())
 }
 
diff --git a/test-data/message/thunderbird_encrypted.eml b/test-data/message/thunderbird_encrypted.eml
new file mode 100644
index 000000000..f5ea542c2
--- /dev/null
+++ b/test-data/message/thunderbird_encrypted.eml
@@ -0,0 +1,80 @@
+From - Fri, 13 Oct 2023 05:36:46 GMT
+X-Mozilla-Status: 0801
+X-Mozilla-Status2: 00000000
+Message-ID: <19925052-21a0-530a-cb93-dd05d227ece2@example.org>
+Date: Fri, 13 Oct 2023 02:36:46 -0300
+MIME-Version: 1.0
+User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
+ Thunderbird/102.13.0
+Content-Language: en-US
+To: bob@example.net
+From: Alice <alice@example.org>
+X-Mozilla-Draft-Info: internal/draft; vcard=0; receipt=0; DSN=0; uuencode=0;
+ attachmentreminder=0; deliveryformat=0
+X-Identity-Key: id3
+Fcc: imap://alice%40example.org@in.example.org/Sent
+Subject: ...
+Content-Type: multipart/encrypted;
+ protocol="application/pgp-encrypted";
+ boundary="------------RT0xHdRXXmnS0UAhLpOJ60ps"
+
+This is an OpenPGP/MIME encrypted message (RFC 4880 and 3156)
+--------------RT0xHdRXXmnS0UAhLpOJ60ps
+Content-Type: application/pgp-encrypted
+Content-Description: PGP/MIME version identification
+
+Version: 1
+
+--------------RT0xHdRXXmnS0UAhLpOJ60ps
+Content-Type: application/octet-stream; name="encrypted.asc"
+Content-Description: OpenPGP encrypted message
+Content-Disposition: inline; filename="encrypted.asc"
+
+-----BEGIN PGP MESSAGE-----
+
+wcDMA/K57StIWPW6AQwAsFW8p7uETMZ3/gSrnnOR6BbRmglj/J9WB95b6h9N66ywcAgemRADi4Zm
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+-----END PGP MESSAGE-----
+
+--------------RT0xHdRXXmnS0UAhLpOJ60ps--