Exactly the same issue here.
The links used to work prior to an Outlook update. Users that are on the monthly channel running version 1811 experience this issue consistently. Users on the semi-annual channel running version 1808 do not have this issue at all.
I think the solution for us will be to change the update channel to semi-annual and downgrade Office. You can do this various ways including GPO and manualy with registry change.
Unfortuantly I haven't found much info regarding this elsewere so I'll be watching this forum closely.