[exim] TLS Cipher list - sorting?

Hi,

i have the requirement that my exim sends outgoing mails with at least
256 bit encryption cipher.
This works for most hosts, but some servers reject my connection because
they say that there would be only a 128 bit encryption cipher.

Is there a possibility how i can sort the cipher list to announce 256 bit
ciphers on client side first?

In my exim4.conf i have:

tls_require_ciphers = NORMAL:!VERS-SSL3.0:!AES-128-CBC

but as i understand this is required only when receiving mails.

Thanks in advanced and greetings!