This script will help you to export all email in your mailbox locally in a folder. (Imap)

exportmail.py

# install imaplib2 before running.
# written for python3
# adjust your IMAP server details!

import imaplib
import email
from email.policy import default
import os

# IMAP server details
IMAP_SERVER = 'your_imap_server'
EMAIL_ACCOUNT = 'your_email_address'
PASSWORD = 'your_email_password'
OUTPUT_DIR = 'emails_backup'

# Create output directory if it doesn't exist
if not os.path.exists(OUTPUT_DIR):
    os.makedirs(OUTPUT_DIR)

def save_email(mailbox, email_id, msg_data):
    for response_part in msg_data:
        if isinstance(response_part, tuple):
            msg = email.message_from_bytes(response_part[1], policy=default)
            
            # Get email subject
            subject = msg['subject'] if msg['subject'] else 'No_Subject'
            subject = "".join([c if c.isalnum() else "_" for c in subject])
            
            # Save email to a file
            mailbox_dir = os.path.join(OUTPUT_DIR, mailbox.replace('/', '_'))
            if not os.path.exists(mailbox_dir):
                os.makedirs(mailbox_dir)
            
            with open(os.path.join(mailbox_dir, f'{email_id.decode()}_{subject}.eml'), 'wb') as f:
                f.write(response_part[1])

# Connect to the server and login
mail = imaplib.IMAP4_SSL(IMAP_SERVER)
mail.login(EMAIL_ACCOUNT, PASSWORD)

# Get all mailboxes
status, mailboxes = mail.list()

if status != 'OK':
    print("Failed to retrieve mailboxes")
    mail.logout()
    exit()

for mailbox in mailboxes:
    mailbox_name = mailbox.decode().split(' "/" ')[1].strip('"')
    print(f"Processing mailbox: {mailbox_name}")

    # Select the mailbox
    status, data = mail.select(mailbox_name)

    if status != 'OK':
        print(f"Failed to select mailbox: {mailbox_name}")
        continue

    # Search for all emails in the selected mailbox
    status, email_ids = mail.search(None, 'ALL')

    if status != 'OK':
        print(f"Failed to retrieve emails from mailbox: {mailbox_name}")
        continue

    # Convert email ids to a list
    email_ids = email_ids[0].split()

    for email_id in email_ids:
        status, msg_data = mail.fetch(email_id, '(RFC822)')
        save_email(mailbox_name, email_id, msg_data)

# Logout and close connection
mail.logout()