[exim] If spamd times out: Mail is accepted but "417 Tempora…

Hi list,

I scan my incoming mails with the ACL directive "spam" and I've set "defer_ok"
It seems to me, that this is not working in any circumstances. Here
are 3 examples:

1) I set spamd_address to an inexistent device
The log says
spam acl condition: warning - spamd connection to 127.0.0.5, port 783
failed: Connection refused
spam acl condition: all spamd servers failed
[...]
Completed

The mail is accepted and all is good

2) I drop the tcp connection with my firewall
The log sasy
spam acl condition: warning - spamd connection to 127.0.0.1, port 783
failed: Connection timed out
spam acl condition: all spamd servers failed
[...]
Completed

The mail is accepted and all is good again

3) My log shows some entries like
spam acl condition: error reading from spamd socket: Connection timed out
[...]
Completed

I was not able to reproduce this error but I think that there are not
enough child processes of spamd available.
According to the sending mailserver, this is what happened:

>> > ErrCode = -162
>> ErrString = End of socket stream data
>> SMAIL SMTP-Send MX = "domain1.tld." SMTP = "domain2.tld" From = "user@???
>> " To = "user@???" Failed !
>> SMTP-Error = "417 Temporary delivery error"
>> SMTP-Server = "domain1.tld."

To my understanding, this mail should have been accepted as in the two
examples before - without sending out a temporary error. Has anyone an
idea what's going wrong here?

Many thanks!