When sending an encrypted mail, eM Client tries to find an encryption certificate by searching for the email address of the recipient. This search is case sensitive
Incoming mails sometimes contain capital letters for name and first name, e.g. John.Doe@gmail.com.
If a certificate is assigned to the address firstname.lastname@example.org, eM Client does not find this certificate.
I tried to add the upper case letter email address to the contact and assign the same certificate. The import works fine, but the certificate is not saved. Obviously, assigning a certificate is only possible for one email address of a contact.
The best solution would be to design the certificate search case insensitive. Instead assigning a certificate to more than one emai address assigned to contact would be helpful.