Exchange 2003 new ISP problem

Just installed a new ISP, created a new MX called  5 , the old ISP is known as which I left as is but set it to 10.
All incoming is fine as expected, but outgoing seem to be an issue,

First I sent out 2 emails from a users account, with a 5 min gap between them, they both sat in the queue with the error :
The connection was dropped due to an SMTP protocol event sink

While I were trying to find answers and test with nslookup and telnet, almost 10 mins after they sat in the queue, they just vanished, and strange as it is, these two emails arrived at my gmail account, so it seem like SMTP must be working, then I tried two more but its almost 20mins and they are still in the queue with the same error as above.

Can someone explain to me what is going on ?
I have PTR set for the new IP against the domain name so not sure what else I can do on this one.
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Patrick BogersDatacenter platform engineer LindowsCommented:

Your SMTP send connector seems to be working, question is why it is not functioning as wanted. How is it configured?
Are there event logs giving more info?
CombemartinAuthor Commented:
The server were working fine with the old ISP except for poor speed, not sure what you meant by how is it configured?
Just restarting the server so should have access to events soon, what should I be looking for ?
Alan HardistyCo-OwnerCommented:
Have you asked your new ISP to configure Reverse DNS on your new fixed IP Address?

If not - you need to or some other Mail Server will reject your connection attempts and mail-flow will suffer as a result.

You can check this has been done on


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Patrick BogersDatacenter platform engineer LindowsCommented:
@Combermartin, Where is your SMTP connector sending the e-mail to(check the adress space)? and look out for SMTP alerts in event logs.

@Alan, poster writes he has PTR records in place, this is called reversed DNS.
Some additional tools you have at (SMTP test)
Patrick BogersDatacenter platform engineer LindowsCommented:
Yes, davorin has also a very good point. You might like this link as well.
Alan HardistyCo-OwnerCommented:
Missed the PTR part of the question (note to self - read the full question before answering)!

My comment about is still relevant though - the new IP may be a dirty IP Address and thus you may need to get it removed from some blacklists before mail-flow returns to normal.
PTR Record
DKIM Record
SPF Record
Blacklist status

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