Peter's Pages Peter's Pages
Apple Mail frequently hangs for minutes, fails to save account changes, autonomously modifies your settings. Too clever by half, feels like they only tested it for Cloud based mail.

Moved ~/Library/Containers/com.apple.mail to backup directory.
Moved to using [https://www.postbox-inc.com/ Postbox] which may not be sexy but is solid (what I want
in a Mail client). I then moved to using my iPad for mail instead.
X11 needs to be installed for applications like ImageMagick.
[https://support.apple.com/en-gb/HT201341 Apple Support] guides one to [https://www.xquartz.org/ XQuartz].
SSH failed to my website after domain moved to new server, complaining about possible spoofing.
Simplest answer is to remove the ''known_hosts'' file in the user's .ssh folder.
AppStore always gives "This item is temporarily unavailable. Try again later." messages.
See threads like [https://discussions.apple.com/thread/6622317 Xcode 6.1 unavailable].
Cleaning the Darwin user cache for the AppStore by:

rm -rf "$(getconf DARWIN_USER_CACHE_DIR)/com.apple.appstore"

may help. Multiple causes.