SMTP delays - Outbound email only

Using Exchange 2003 SP2 on an SBS2003 SP2 server. Mail is sent/received via SMTP. Receiving of emails is 100% fine, but sending of emails seems to have developed a problem that I can see no reason for. A good proportion of email gets sent okay, but also quite a few become delayed and sometimes do not get delivered at all. I have tried configuring the SMTP connector to send via DNS and via our ISPs mail relay, but I have the same problem, particularly with emails that have attachments. My domain does not appear to be blacklisted, or on any spam lists. I also have GFI Mail Security running (mail virus checking software) and GFI Mail Essentials (spam checking software) but these are only checking INCOMING mail. There have been no major changes to the system or network, and I'm starting to pull my hair out in frustration at not being able to find a reason. Any help or advice would be much appreciated.
Alan_ButlerAsked:
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vishal_impactCommented:
HI
did you tried restrating the smtp connector and virtual server this will be the first step i will do .
then try to do traceroute to your isp and see how much time it takes to reach to isp and not the time to each destination on this route make sure small delays on small scale may delay mail on some time .
check your router and gateways settings and contact your isp to check if there is any broken link down from your server to their end as this is the last possibility ..
as if emails are going out with delay its a network issue not server issue for sure
let me know the outcome of this tests
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Alan_ButlerAuthor Commented:
Vishal
I have tried even deleting and recreating the SMTP connector. The trace route to my ISP takes only milliseconds, so no network issue it would seem.
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vishal_impactCommented:
hi
just to confirm can you explain me how you are sending outbound emails
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Alan_ButlerAuthor Commented:
Emails are being sent via the Default SMTP connnector, to a smart host (our ISPs which is post.demon.co.uk)
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Alan_ButlerAuthor Commented:
There are no issues with this smart host at present either, as I am able to Telnet to port 25 okay
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vishal_impactCommented:
HI
OK i think is something with your smarthost or mx records can you confirm you have all correct record in your mx records
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Michael WorshamStaff Infrastructure ArchitectCommented:
Goto DNSStuff.com and run a DNSReport on your domain. It can check to make sure your DNS records are correctly setup as well as the MX records. It also checks your e-mail environment just in case there are any underlying issues.
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Alan_ButlerAuthor Commented:
Well everything checked out okay, I changed to sending via DNS and I have been going through ALL my SMTP connection details, Exchange configuration etc etc ....... and discovered that somehow TLS encryption had been enabled on the SMTP connector!!!!! GAH! Which of course many of the receiving mail servers were not configured for TLS connections. Outbound mail is now flowing nicely again, phew!

Sorry to have wasted your time, but your comments were at least helpful in checking out some vital info and thanks for your help people.
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