Re: Sudden problems receiving mail - 550 errors in SMTP logs

Tech Tip: Click here to run a free scan for Windows Errors and optimize PC performance

Have you found any answers when you Googled mailbox unavailable 550?
http://ask-leo.com/why_does_email_bounce.html

I would do a telnet internally to see what you get.
http://support.microsoft.com/kb/153119

On Thu, 03 Apr 2008 11:56:01 GMT, "Paul Kelly" <junk@xxxxxxxxxxx>
wrote:

I have an SBS2003 Std server (used at home) with 6 domains configured for
email - two "live" and the rest test/mess domains.

I have a cable router with dynamic IP so I have a number of services from
DynDNS comprising a couple of DNS zones, some hostnames & "MailHop Forward"
service for my primary DNS zone. The later I have in place to manage the
sheer amount of spam hitting my domain (last time I checked it was >50k
mails per day!). I also use the Internet Message Filtering module as well as
GFI MailEssentials. The router is configured to update my DNS IP's whenever
it changes (rarely).


The basic setup is this:



I have a "formal" domain registered - let's say "mydomain.com". I also have
a "Hostname" registered @ DynDNS, let's say "mydomain.homeip.net". The
domain & hostname is configured with the external IP of my router.



I use the MailHop Relay service to add *specific* email addresses based at
the formal domain, & forward them to email addresses at the "hostname".



e.g. fred@xxxxxxxxxxxx would be forwarded automatically (& transparently) to
fred@xxxxxxxxxxxxxxxxxxxx



I also have my Default SMTP Virtual Server to accept emails *only* from
specific IP addresses & domains (i.e. DynDNS mailhop servers plus a few
others for testing).



Within my recipient policies I have all my domains configured.



What this ultimately means is, if I don't configure an email address within
mailhop forward, then it's discarded. So I effectively have a "whitelist"
email address. I did this after trying to just utilise the "discard emails
for mailboxes that don't exist" within my spam filter but it was getting
constantly hit with spam & the HD rattling was driving me crazy!



The server is fully patched to SP1 with all subsequent updates with the
exception of IE7. (I havent yet taken the plunge with SP2 on an SBS box).



****The above solution has worked *perfectly* for at least two years.*****



I noticed yesterday that I hadn't had any mail for a couple of days so
looked into it. First thing was to check the IMF UCE Archive folder to see
how much was in there since I last cleared it about 4/5 days previously. It
was empty - most unusual!



I then checked all mail services were running & they were. I rebooted the
server just to give it a refresh (hadn't been rebooted for a couple of
months) which didn't seem to make a difference.



I was assuming that there was a DNS issue or something (perhaps I'd missed a
renewal or something) so checked all that out.



Then I decided to check the SMTP log files and found that emails were
hitting the SMTP server, but were then getting dropped with a 550 error!
(Mailbox Unavailable). This is *all* emails, for *all* mailboxes, not just
my own.



Closer analysis of the SMTP logs showed that this started happening some
time between 01:39 & 04:56 on 1st April - the first was that timestamp of
the last correctly delivered email, the second was the next email which
replied with a 550 error.



I know I was in bed at this time so hadn't made a change. There was no
server reboot in the event log around that time so it's not as though there
was a "delayed" change which only took place after a reboot.



So, in summary, mails are correctly routed to my server for my domain, but
the SMTP service is dropping them claiming they have no mailbox to deliver
to. It isn't my spam solutions dropping them because they aren't getting
that far.



I haven't applied any MS updates this week and can't think of any other
changes I've made this week either.



I'm stuck now as to where to look from here to figure out what's going on!



Can anyone suggest where to look next as I'm at a loss!



Regards,



Paul

See what SBS support is working on
http://blogs.technet.com/sbs/default.aspx
Check your SBS with the SBS Best Practices Analyzer
http://blogs.technet.com/sbs/archive/tags/BPA/default.aspx
.

Relevant Pages

  • Re: POP3 Is not working
    ... > the POP3 service for email. ... > SMTP services so that when errors occur, ... > SMTP virtual server as I made some mistakes in setting it up and there ... > POP3's mailbox directory is 'mailbox' with a single mailbox setup ...
    (microsoft.public.windows.server.sbs)
  • Re: Routing emails between internal exchange servers
    ... internally (from a mailbox on one server to a mailbox which is on the ... second) are being routed via the smtp gateway. ... destined for the Internet will go to the FE. ...
    (microsoft.public.exchange.connectivity)
  • Re: POP Connector to SMTP retrieval
    ... Connector collection to SMTP delivery collection - before I make the ... Whoever runs that server would need to configure ... points to the IP of the mailbox on the external web server and set ...
    (microsoft.public.windows.server.sbs)
  • SBS 2k3 SMTP "Messages Pending Submission"
    ... Incoming mail stuck in SMTP "Messages Pending Submission" ... For some weeks now have SBS 2k3 Premium server that on reboot will get ...
    (microsoft.public.backoffice.smallbiz2000)
  • Re: Configuring SMTP in IIS 6.0 Questions
    ... That won't do if the mailbox server is actually elsewhere. ... delivery as I want all emails that hit this SMTP server to make outbound SMTP ... will relay authenticated submissions to its Remote domains -- provided ...
    (microsoft.public.inetserver.iis.smtp_nntp)