How to force Mail to use new email certificates instead of still valid one?
In response to a warning SwissSign that my certificates for three email accounts will expire in 10 days I purchased and installed new certificates on my MacBook Pro 15" 2018 running macOS 10.13.6. The certificates are in the Keychain and they are valid. I have also installed them on my iPhone and iPad Pro and, on those two devices, can force Mail to use them instead of the still valid old ones. Is there any way to do the same on the Mac? If there is, it is well hidden and would seem to be inconsistent with Apple's security consciousness. By switching now I would like to avoid (a) any confusion on the part of recipients of my signed emails as to the use of two different certificates for each account, depending on the hardware from which the emails were sent, (b) the eventual failure of macOS to "automagically" switch to the new certificates when the old ones expire.
MacBook Pro with Touch Bar