iLetter version 2.0 is a rewrite of iLetter as you have been using it, written as a single application with no other software components needed. It is written using the Xojo Integrated Development Environment.
As previously, it should sit in the same folder as your iLetterData folder (not in the Applications folder). It is available now for macOS, distributed as a disk image (.dmg), and for Windows7/Windows10 as a ZIP file.
If you have been running iLetter v1, and therefore already have a set of mailboxes, please ensure you use the final version of iLetter v1 (1.12.2) and run that at least once before using iLetter v2.
This release of iLetter has been code-signed, and it should therefore open under macOS Sierra and later without issue. If you find this not to be the case, please let me know.
The User Guide has been updated to reflect some changes and improvements between iLetter v1 and v2. The changes are summarised in Appendix 2 of the Guide. There are not that many, as the intention up to this point has been to duplicate existing functionality. Once v2 has bedded down then other changes can be considered.
Please update me with any information about crashes or other unexpected behaviour. In such cases please send me your log file and what you were doing at the time the problem occurred.