The issue requests a new `tls1 3` option for TLS 1.3 support. Investigate the current SSL implementation in offlineimap (likely in the IMAP folder). The project uses Python's ssl module; check for compatibility with OpenSSL 1.1.1 and whether TLS 1.3 constants are available. Note that the repository is marked as LEGACY and recommends moving to offlineimap3, which may already support this. Review the linked OpenSSL wiki page for details on TLS 1.3 support.