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apitsos
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IMAP connections are slow from outside

Mon May 16, 2022 4:38 pm

Hi there,

It's been a while I am facing an issue with a mail service we are hosting under our new infrastructure in a datacenter. The problem I am facing is that the IMAP connections are really very slow from outside, but when accessing the IMAP service from within the same network, the connection is much more faster.

I can see that also under the "traffic" of the relevant firewall rule, as established connection. When the connection is from the same network, it hits really good speed (about 100 Mbps). But from outside is limited to 6-7 Mbps only. Of course the problem is not the Internet connection, as it is Gigabit and in addition the datacenter confirmed that they are not applying any limitations or restrictions on our connection.

At the beginning I also thought that the problem is also relied on the software we use as mail server, but as explained, tests shown already that the same server responds pretty nice if access from a virtual machine on the same network/infrastructure.

Is anyone here experiencing similar issues, or could someone assist me on this strange problem I am facing? I can't think anything I could try on the firewall in order to solve that puzzle.

Please note the device is a MikroTik CCR1009-7G-1C-1S+.

Thanks a lot in advance!


With kind regards,
Angelos Pitsos
 
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Larsa
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Re: IMAP connections are slow from outside

Tue May 17, 2022 1:13 am

It might depend on type of authentication and encryption as well as what message store being used for IMAP.

If for example MS Exchange Server installed on premise as a hybrid it might have some issues a regarding this thus you need to test the connections in exactly the same way regardless of whether it is done locally or through internet. Please supply some more detaljs regarding the setup if you want some more assistans.
 
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apitsos
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Re: IMAP connections are slow from outside

Tue May 17, 2022 1:52 am

Hi Larsa,

Thanks a lot for your answer. I have a MailEnable server installed in a Virtual Machine in my our own infrastructure in the datacenter. When trying to test an IMAP connection with a tester I have, I am getting the following results:
  • Locally (localhost): 5-8 Mbps
  • From outside the datacenter (public network): 5-8 Mbps
  • From inside the datacenter's network (from another VM on the same network): 100-200 Mbps
What I can't understand, is how is possible to have such a low speed on localhost. Within the same server. But of course this is not related with these forums.

Now, I was wondering if there is anything I could do in order to check if the MikroTik firewall is responsible for the slow IMAP connections from the public network.

It also doesn't make sense, that IMAP connection to another web server from outside is really extremely fast, at about 200 Mbps.


With kind regards,
Angelos Pitsos
 
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apitsos
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Posts: 35
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Re: IMAP connections are slow from outside  [SOLVED]

Tue May 17, 2022 12:24 pm

Hi there,

I just wanted to give some feedback here. Finally the problem was solved, but it was not network related. The problem was on the IMAP service of MailEnable. The development team of MailEnable spent the last day trying to make improvements and finally they replaced the IMAP service on our server and we saw some improvement.

I would like to thank anyone who spent time reading or answering this thread.


With kind regards,
Angelos Pitsos
 
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Larsa
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Re: IMAP connections are slow from outside

Tue May 17, 2022 12:38 pm

Great you managed to locate and fix the issue! In my experience similar problems are usually related to application software as in your case. Good luck with the newly installed imap services!
 
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apitsos
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Posts: 35
Joined: Tue Feb 22, 2022 9:36 pm
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Re: IMAP connections are slow from outside

Tue May 17, 2022 12:52 pm

Great you managed to locate and fix the issue! In my experience similar problems are usually related to application software as in your case. Good luck with the newly installed imap services!
Thank you so much! Wishing you a great day... :)

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