Citi has brought back the Secure Message feature to their Citi Cards online login. It’s quite possibly a temporary thing due to Covid-19 customer response.
Contact Us (bottom of page) > Secure Message Center > Send a Message
Citi removed the Secure Message option back in 2018, leaving phone or chat as the contact options. Now, Secure Messages is an option as well. (Some have had Secure Messages as an option all along.)
[Update 4/24/20: seems like now the SM option only works for COVID-19 concerns.]
Hat tip to reader Bkkk
