The main forum for community discussion and support is the ITK discourse space. It is an incredibly valuable discussion forum, with very low noise and very high signal. It is frequented by the core ITK developers, regular users and new users alike.
To subscribe to the civilized discussion, follow the instructions at getting started guide.
ITK transitioned from a traditional mailing list to the discourse platform on September, 21 2017.
The full archives of the previous mailing lists are available from:
It is a good idea to search here first before asking questions, to make sure it hasn't come up before. There are many detailed explanations and discussions contained in the archive, so it is well worth reading. It is also a good idea to check the FAQ and do a search on this site.
If you are asking a question about building ITK, please include the following information at a minimum:
The more information you include in your original post, the easier it will be for us to help you.