Currently you can not select a value greater than 99.99kB in the search field "Size in Bytes" in the search dialog. The maximum value should be at least 1TB (like in thunderbird). Example use case: Your quota is reached and you have to delete the biggest mails.
Git commit 31bc908dc46927cea82780f71d7cec76951a993e by Montel Laurent. Committed on 20/10/2017 at 04:56. Pushed by mlaurent into branch 'master'. Fix Bug 385967 - Increase maximum value for "Size in Bytes" in search FIXED-IN: 17.12.0 M +1 -0 src/search/widgethandler/numericdoublerulewidgethandler.cpp https://commits.kde.org/mailcommon/31bc908dc46927cea82780f71d7cec76951a993e