Python 更改电子邮件附件名称和扩展名

Question

我发送带有 .xlsx 文件的电子邮件的代码是

from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText
from email.mime.base import MIMEBase
from email import encoders
import smtplib

msg = MIMEMultipart()
msg['From'] = "..."
msg['To'] = "..."
msg['Subject'] = "..."
msg.attach(MIMEText("..."))

part = MIMEBase('application', "octet-stream")
part.set_payload(open(myfilename, "rb").read())
encoders.encode_base64(part)
part.add_header('Content-Disposition', 'attachment', filename="Attachment.xlsx")
msg.attach(part)

smtp = smtplib.SMTP('...')
smtp.sendmail(msg['From'], msg['To'], msg.as_string())
smtp.quit()

它成功发送电子邮件。然而，附加文件具有随机名称，如带有“.dat”扩展名的“attiaf9l”。可能是什么问题？