Client certificate not saved for outgoing mail server

Hello everyone,

When I choose the certificate that I have installed on android OS, K-9 Mail acknowledges that it exists and lets me select it. It proceeds to tell me that the new settings have been saved, and that my certificate will be used for my e-mails from now on; however, when I go back into the “send e-mail” setting for my account, it is no longer selected, and the e-mails are sent without using the certificate. K-9 Mail has had no problems accepting my certificate for the incoming mail server, but not for the outgoing, despite the fact that this worked flawlessly on thunderbird. I would appreciate your help!