How to fix AttributeError: 'list' object has no attribute 'encode'

I'm trying to send a mail with an html attachment which contains a table from a Pandas dataframe and some plotted images in Python 3.7. When the data in the provided dataframe is not null and therefore there are plotted images to send, i wont run into the error. I also collect occuring errors in a list and add them to the final string which i want to sent with the mail.

def mailMe():

    # Create the container email message.
    msg = EmailMessage()
    msg['Subject'] = 'Mail'
    msg['From'] = sender
    msg['To'] = receiver

    #style overview table
    htmlTable = (
        df.style
        .set_table_styles(styles)
        .applymap(color_negative_red)
        .set_caption('Auswertung')
        .render()
    )

    #attach 100 dpi images
    if not len(pngfiles100)==0:
        for file in pngfiles100:
            try:
                with open(r'.\\temp\\'+file, 'rb') as fp:
                    img_data = fp.read()

                msg.add_attachment(img_data, maintype='image',
                                            subtype=imghdr.what(None, img_data),
                                            filename=file)
            except:
                continue

            fp.close()        

    #Error messages
    htmlTable+='\n'+'<p style="font-family:Arial;"><b>Errors:</b></p>'
    if not len(errors)==0:
        for i in errors:
            htmlTable+='\n'+'<p style="font-family:Arial;">'+i+'</p>'


    pngFolder=r'.\\temp\\' 
    htmlTable+=""" 
    <table>
    <tbody>
    """

    i=0
    for col in df.columns:
        tempDf=pd.DataFrame(data=df[col])
        tmpHtml = (
            tempDf.style
            .set_table_styles(styles)
            .applymap(color_negative_red)
            .render()
            )
        if not len(pngfiles50)==0:
            #embed 50 dpi images in mail
            htmlTable+=u'\n'+'<tr><td>'+tmpHtml+'</td>'+'<td><img src="cid:image'+str(i+1)+'"></td></tr>'+u'\n'
            try:
                fp=open(pngFolder+pngfiles50[i],'rb')
                msgImage = MIMEImage(fp.read())
                fp.close()
                msgImage.add_header('Content-ID','<image'+str(i+1)+'>')
                msg.attach(msgImage)
            except:
                continue
            i+=1

    htmlTable+="""
    </tbody>
    </table>
    """

    # Send the email via our own SMTP server.
    with smtplib.SMTP(host) as s:
        htmlTable = MIMEText(htmlTable,"html")
        msg.attach(htmlTable)
        s.send_message(msg)

Traceback:

Traceback (most recent call last):
  File "c:\Users\mmai\.vscode\extensions\ms-python.python-2019.8.30787\pythonFiles\ptvsd_launcher.py", line 43, in <module>
    main(ptvsdArgs)
  File "c:\Users\mmai\.vscode\extensions\ms-python.python-2019.8.30787\pythonFiles\lib\python\ptvsd\__main__.py", line 432, in main
    run()
  File "c:\Users\mmai\.vscode\extensions\ms-python.python-2019.8.30787\pythonFiles\lib\python\ptvsd\__main__.py", line 316, in run_file
    runpy.run_path(target, run_name='__main__')
  File "C:\Users\mmai\AppData\Local\Programs\Python\Python37-32\lib\runpy.py", line 263, in run_path
    pkg_name=pkg_name, script_name=fname)
  File "C:\Users\mmai\AppData\Local\Programs\Python\Python37-32\lib\runpy.py", line 96, in _run_module_code
    mod_name, mod_spec, pkg_name, script_name)
  File "C:\Users\mmai\AppData\Local\Programs\Python\Python37-32\lib\runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "c:\Users\mmai\Documents\Python\Mail.py", line 1043, in <module>
    OEM()
  File "c:\Users\mmai\Documents\Python\Mail.py", line 168, in __init__
    self.mailMe()
  File "c:\Users\mmai\Documents\Python\Mail.py", line 1035, in mailMe
    s.send_message(msg)
  File "C:\Users\mmai\AppData\Local\Programs\Python\Python37-32\lib\smtplib.py", line 964, in send_message
    g.flatten(msg_copy, linesep='\r\n')
  File "C:\Users\mmai\AppData\Local\Programs\Python\Python37-32\lib\email\generator.py", line 116, in flatten
    self._write(msg)
  File "C:\Users\mmai\AppData\Local\Programs\Python\Python37-32\lib\email\generator.py", line 181, in _write
    self._dispatch(msg)
  File "C:\Users\mmai\AppData\Local\Programs\Python\Python37-32\lib\email\generator.py", line 214, in _dispatch
    meth(msg)
  File "C:\Users\mmai\AppData\Local\Programs\Python\Python37-32\lib\email\generator.py", line 427, in _handle_text
    if _has_surrogates(msg._payload) and not self.policy.cte_type=='7bit':
  File "C:\Users\mmai\AppData\Local\Programs\Python\Python37-32\lib\email\utils.py", line 57, in _has_surrogates
    s.encode()
AttributeError: 'list' object has no attribute 'encode'

It seems there is a problem with s.send_message(msg) but i can't wrap my head around it. Sender and receiver are both a string and not a list.

Solved it by adding msg.add_attachment(htmlTable)