Just installed a new ISP, created a new MX called mail4.company.com 5 , the old ISP is known as mail2.company.com 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.