Own mail address in heading replaced by "Ik"

Hello,

My wife and I both use Kmail 18.12.3 on openSUSE 15.1.

My wife complains that, wherever her e-mail address should be in mail headers, 
this is replaced by the string "Ik" (which is Dutch for "I").

I do not see this in my case, thus it must be able to switch off this 
"feature". But I can not find it anywhere.

Any ideas?
-- 
Met vriendelijke groet,
Henk van Velden