We have two separate, stable systems running Exim+Mailscanner in the
separate
process mode (-bd incoming, -q1m outgoing, with Mailscanner in the
middle).
A couple of days ago one (only) of the systems started showing a
strange symptom.
Most (but not all) traffic from outside was being refused with:
"451 rejected: temporarily unable to verify sender address ..."
Since this wasn't due to disk space or system load, there was no
apparent reason.
Today I turned on Exim -d11 debugging to see exactly what was
happening.
Below are extracts from a typical incoming transaction (edited as
nec.),
one of many external domains affected. It's Exim 3.36.
What concerns me is this line, which seems to be the error which gives
rise to
the 451 status:
"temporary error while verifying xxxx@??? - will give
error after DATA"
What IS the temporary error? It's not a file read/write problem with
the db/reject
database - that gets updated OK a little later on.
++++
As per the Mailscanner instructions, the key settings in the
Exim config. are (config. fragments):
queue_only = true
defer_director:
driver = smartuser
new_address = :defer:
defer_router:
driver = domainlist
self = defer
route_list = "* 127.0.0.1 byname"
++++
The debugging output (suitably edited):
[...]
routing xxxx@???, domain thurrock.gov.uk
defer_router router called for xxxx@???
route_domain = thurrock.gov.uk
routelist_item = * 127.0.0.1 byname
after handling route_lists items, matched = 1
original hostlist=127.0.0.1 options=byname
expanded hostlist="127.0.0.1" options=byname
local host found for non-MX address
fully qualified name = 127.0.0.1
127.0.0.1 127.0.0.1 mx=-1
defer_router router deferred thurrock.gov.uk
message: remote host address is the local host
locked /data/exim/spool.in/db/reject.lockfile
opened DB file /data/exim/spool.in/db/reject: flags=2
dbfn_read: key=xxxx@???:mail1.messagelabs.com
temporary error while verifying xxxx@??? - will give error
after DATA
SMTP>> 250 <xxxx@???> is syntactically correct^M
SMTP<< RCPT TO:<xyz@???>
abc.ac.uk in local_domains? no (end of list)
abc.ac.uk in relay_domains? no (end of list)
local host found for non-MX address
localhost 127.0.0.1 mx=-1
host in host_accept_relay? no (end of list)
DNS lookup of abc.ac.uk (MX) succeeded
local host in list - removed hosts:
mail.camford.ac.uk 212.219.52.55 10 [the exim host]
host_find_bydns yield = HOST_FOUND (2); returned hosts:
mail.abc.ac.uk 212.219.52.155 1 158
domain is MXed to this host
[...]
search_tidyup called
locked /data/exim/spool.in/db/reject.lockfile
opened DB file /data/exim/spool.in/db/reject: flags=42
dbfn_write: key=xxxx@???:mail1.messagelabs.com
LOG: 3 MAIN REJECT
rejected from mail1.messagelabs.com [212.125.75.4.51216]:
temporarily unable to verify sender address <xxxx@???>
(try later)
SMTP>> 451 rejected: temporarily unable to verify sender address
<xxxx@???> (try later)^M
search_tidyup called
set_process_info: 7458 handling incoming connection from
mail1.messagelabs.com [212.125.75.4.51216]
ready for new message
