[exim] Retry interval with multiple mx

Hello,
i have a question to retry intervals of deferred messages.

As far as i could see, if exims tries to send a message and receives a
temporal error (deferred), all further messages to the same recipient
are freezed until the retry interval is expired. This was observed with
only one MX entry.

I assume that a second delivery attemp will be started immediately if a
second mx is present.

What will happen if the second mx points to the same ip as the first?
Does exim uses the name or the ip to maintain retry intervals?
MX mx1.domain.de
MX mx2.domain.de
mx1.domain.de -> 1.2.3.4
mx2.domain.de -> 1.2.3.4


Reason for this question:
I have trouble sending mail to an MX pool. There is only one MX entry
with one IP-adress. But behind the IP-adress, there is a pool of
multiple mail servers. But if the sending mail server receives a
deferred message, it is not trying another server.
(i cannot change this setup)
Thanks
Andi