diff --git a/tests/test_utils_sendmail.py b/tests/test_utils_sendmail.py
new file mode 100644
index 00000000..8bb00055
--- /dev/null
+++ b/tests/test_utils_sendmail.py
@@ -0,0 +1,42 @@
+import os
+import subprocess
+import getpass
+from email.mime.text import MIMEText
+import sys
+sys.path.insert(0, os.path.abspath(os.path.join(os.path.dirname(__file__), '..')))
+from slic.utils.sendmail import *
+
+def test_sendmail_mime_format_in_tmux():
+    # Retrieve the tmux TTY from the environment
+    tmux_tty = os.environ.get("TMUX_TTY")
+    assert tmux_tty and os.path.exists(tmux_tty), f"Invalid TMUX_TTY: {tmux_tty}"
+
+    # Define test message parameters
+    from_addr = "robot@local"
+    subject = "MIME Format Test"
+    body = "This is the MIME body."
+
+    # Send the message via your sendmail()
+    sendmail(
+        to_addr=f"| tee {tmux_tty}",  # Write the message to the tmux terminal
+        from_addr=from_addr,
+        subject=subject,
+        body=body
+    )
+
+    # Capture the content from the tmux terminal
+    output = subprocess.check_output(
+        ["tmux", "capture-pane", "-pt", "test-session"],
+        timeout=2
+    ).decode()
+
+    # Build the expected MIME-formatted message
+    msg = MIMEText(body)
+    msg["To"] = to_addr
+    msg["From"] = from_addr or getpass.getuser()
+    msg["Subject"] = subject
+    expected = msg.as_string()
+
+    # Verify that each line of the expected MIME message is present in the tmux output
+    for line in expected.splitlines():
+        assert line in output, f"Missing line in tmux output: {line!r}"
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