You can try an offlineimaprc file like below:

[general]
accounts = Email-Sync

[Account Email-Sync]
remoterepository = old_server
localrepository = new_server

[Repository old_server]
type = IMAP
remotehost = poczta.o2.pl 
remoteuser = u_s_e_r
maxconnections = 1
readonly = true
folderfilter = lambda folder: folder not in ['Trash']

[Repository new_server]
type = IMAP
remotehost = imap-mail.outlook.com
remoteuser = user@outlook.com
ssl = yes
maxconnections = 1
cert_fingerprint = c914dd966dbd0912c36ec294f83d8d3b5a434729
createfolders = false

If you get a message with invalid ssl cert, just update/insert the line with a proper value of cert_fingerprint. It shoud be next to the error message