[Exim] temporary error taken as permanent error?

Oddly enough today a quite normal (but not in the last two days)
temporary error with smtpX.libero.it has generated immediately a
permanent error failure:

[below I deleted the local_part from the address]

2003-06-11 12:11:36 HGBDR7-0004RQ-KG SMTP error from remote mailer
after initial connection: host mx5.iol.it [193.70.192.90]: 421
smtp7.libero.it Service not available - too busy
[identical, mutata mutandis, entries for the other MXes]
2003-06-11 12:11:36 HGBDR7-0004RQ-KG == @iol.it R=dnslookup
T=remote_smtp defer (0): SMTP error from remote mailer after initial
connection: host mx5.iol.it [193.70.192.92]: 421 smtp8.libero.it
Service not available - too busy
2003-06-11 12:11:36 HGBDR7-0004RQ-KG ** @iol.it: retry timeout exceeded

and the bounce:

This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

   @iol.it
     SMTP error from remote mailer after initial connection:
     host mx5.iol.it [193.70.192.92]: 421 smtp8.libero.it Service not
available - too busy:
     retry timeout exceeded
[...]

what the heck, this is my retry configuration:

begin retry

# Domain               Error       Retries
# ------               -----       -------

*                      *           F,2h,15m; G,16h,1h,1.5; F,4d,6h

and exim is run as exim -bd -q15m

What is going on?

Thanks

Giuliano
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