The manual pages are the finest way to document the software, mailing lists are used for discussions.
Web manual pages are available from OpenBSD.
The OpenBSD project provides various mailing lists for all matters of the operating system, including its subprojects like relayd. Use the mailing lists to discuss relayd and httpd, to submit patches or the share bugs.
Discussion of technical topics for OpenBSD developers and advanced users. This is not a "tech support" forum, do not use it as such. OpenBSD developers will often make patches to implement new features and other important changes available for public testing through this list.
Various other topics and details about the netiquette are found on OpenBSD's Mailing Lists page. Subscribe to "source-changes" to follow all source tree changes or to "announce" for important announcements.