Very simple Python script to download/upload emails from/to an IMAP folder.

migrate_imap.py

#!/usr/bin/env python
#
# Very simple Python script to download/upload emails from/to an IMAP folder.
# This code is based on a simpler version from https://gist.github.com/robulouski/7442321
# This code is released into the public domain.
#
# Paloha 2020
# khachuy2705 2025: Preserve the timestamp of the email message
import os
import sys
import imaplib
import getpass
import eml_parser
ep = eml_parser.EmlParser()

LOCAL_DIRECTORY = 'tmp'  # Must be created manually

# Download config
DO_IMAP_SERVER = 'imap.example.com'
DO_EMAIL_ACCOUNT = '[email protected]'
DO_EMAIL_FOLDER = 'INBOX.FolderToBeDownloaded'

# Upload config
UP_IMAP_SERVER = 'imap.example.com'
UP_EMAIL_ACCOUNT = '[email protected]'
UP_EMAIL_FOLDER = 'INBOX.FolderToUpload'

MODE = ['DOWNLOAD', 'UPLOAD'][int(input('Select mode: 0 for download, 1 for upload: '))]
PASSWORD = getpass.getpass()


def mailbox_login(server, account, password):
    M = imaplib.IMAP4_SSL(server)
    M.login(account, password)
    return M


def main():
    print(f'Mode: {MODE}')

    if MODE == 'DOWNLOAD':
        M = mailbox_login(DO_IMAP_SERVER, DO_EMAIL_ACCOUNT, PASSWORD)
        rv, data = M.select(DO_EMAIL_FOLDER)
        if rv == 'OK':
            print('Downloading from: ', DO_EMAIL_FOLDER)
            rv, data = M.search(None, 'ALL')
            if rv != 'OK':
                print('No messages found!')
                return
            for num in data[0].split():
                rv, data = M.fetch(num, '(RFC822)')
                if rv != 'OK':
                    print('ERROR getting message', int(num))
                    return

                fname = os.path.join(LOCAL_DIRECTORY, f'{int(num)}.eml')
                print(f'Writing message {fname}')
                with open(fname, 'wb') as f:
                    f.write(data[0][1])
            M.close()
        else:
            print('ERROR: Unable to open mailbox ', rv)
        M.logout()

    if MODE == 'UPLOAD':
        # Login and check if folder exists
        M = mailbox_login(UP_IMAP_SERVER, UP_EMAIL_ACCOUNT, PASSWORD)
        available_folders = list(map(lambda x: x.split()[-1].decode(), M.list()[1]))
        assert UP_EMAIL_FOLDER in available_folders, 'IMAP folder not on server.'
        print(f'Uploading to: {UP_EMAIL_FOLDER}')

        # Open all .eml files in desired dir and upload them to the server
        eml_fnames = [f for f in os.listdir(LOCAL_DIRECTORY) if f.endswith('.eml')]
        failed_uploads = []
        for i, eml_fname in enumerate(eml_fnames):
            with open(os.path.join(LOCAL_DIRECTORY, eml_fname), 'rb') as eml:
                print(f'Uploading email {eml_fname} | {i+1}/{len(eml_fnames)}')
                eml_read = eml.read()
                try:
                    parsed_eml = ep.decode_email_bytes(eml_read)
                    rv, message = M.append(UP_EMAIL_FOLDER, None, parsed_eml["header"]["date"], eml_read)
                except Exception as e:
                    rv = 'ERR'
                    message = e
                if rv != 'OK':
                    failed_uploads.append(eml_fname)
                    print('ERROR uploading message.')
                    print(message)
        print('Upload complete')
        print(f'{len(failed_uploads)} failed uploads.')
        print(failed_uploads)
        M.logout()


if __name__ == '__main__':
    main()