Is there a mail client supporting user certificates ?



first post for me on this forum. I have the following problem:
the mail server in my institute requires my personal certificate (.p12) to be presented when I am sending mails outside of my internal network (for example from home).
This is easily done when using mail client like thunderbird on linux which allows importing my personal certificate inside it.
But unfortunately this option seems not to be present in the mail client applications for android (I tried with the native mail client as well as k-9 on my new Samsung Galaxy tab 10.1). As a result I cannot send mails from my mail account (while I have no problem in seeing incoming mails).
Is there any mail client supporting certificates to identify myself to the mail server ? Or do you have any other suggestions ?
BTW, my outgoing mail setting (TLS, port 587) should be correct. When I try to send mail being inside my local network I have no problems.

If other details are needed pls let me know. Thanks in advance for any hint!