International network has an error connecting to port 25

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vanthoi_it
Posts: 2
Joined: Tue Jun 06, 2017 9:47 am

International network has an error connecting to port 25

Post by vanthoi_it »

I just installed a Zimbra mail server. I tested sending mail internally, sent from a number of domestic suppliers.
All send and receive normally. But when I use international providers like Gmail or Hotmail, Yahoo, ...
Most of them get an error that can't connect to port 25.
Hotmail just needs to wait a bit, mail can be sent and received normal.
I have tried telnet mail.domain.com 25,465,587
all ports are working when I test on my another server.
I also try to check smtp on https://mxtoolbox.com/ all green, sometimes it warns connection time.
PTR Domain I have also fully pointed.
I also contacted the ISP, they said not to block any ports from my IP either.

Can anyone help me with a suggestion to solve this error?
Thanks1
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