In Evolution I set up a second account which only sends email, to create a alias using the GMail "+" trick. That is, my main Evolution account is something like
firstname.lastname@example.org and the alias account is like
john.doe+FOOBAR@gmail.com. Upon creating the alias account Evolution sent me to GMail to log in for an OAuth token, I tested the account and it worked just fine.
However, now that I've logged out of my desktop and back in again, every attempt to send from the alias account gets the error. The full error from the log journal is:
evolution-sourc: Remote error from secret service: org.freedesktop.DBus.Error.ServiceUnknown: The name :1.734 was not provided by any .service files
I can send emails just fine with my original/default Evolution account.
I'm using Fedora 28 and KDE.
EDIT: Looks like it might be due to this gnome keyring bug. Unfortunately there's no suggested workarounds. I tried replacing the gnome keyring daemon with
gnome-keyring-daemon --replace --blah --blah, but that didn't help.