Issue Outlook mail not working

[Rens]

Hey All,

When my clients add their mail account to Outlook on Windows they get an error with something like "server refused to connect" when i add the same account to my Outlook on Mac nothing is wrong and it works.

I already changed the hostname of imap and smtp but it won't connect. Anyone has the solution for this?

Greetings,
Rens

 

[Ales]

In general, Outlook has no issues when connecting to Plesk mail servers, possible misconfigurations aside.

More information is required in order to help troubleshooting this. For starters, your OS & version, Plesk version, and which mail servers do you use with Plesk? Which Windows and Outlook version is used?

Which mail server names are used by your client to connect, mail.example.com where example.com is the customer's domain or are they using your server's hostname?

Does the hostname have a valid SSL cert and have you set up this SSL cert to secure your mail servers in Plesk?

Which protocols (POP3, IMAP,..) are set in Outlook, which ports?

Can this client use the webmail to log in sucessfully?

All this being said, we usually offer remote or on-site services to our clients to help them resolve such issues, as this is bound to be a configuration problem. If you plan to have customers and need to offer user support to them, I suggest organizing something like that.

 

[Rens]

Hey Ales,

Debian 9.9‬, Version 17.8.11 Update #63, Dovecot, Windows 10 and the latest update of Office 365 with Outlook so 2016?

We tried mail.customersdomain.tdl we tried hostname mail.hostname.tdl

The hostname has a let's encrypt SSL and also we selected the hostname as certificate for securing mail.

They are using imap ports we tried: 143, 993

The client can login with webmail

 

[Ales]

OK, so assuming your Plesk has conventional settings, then this should be a correct value for the IMAP server in Outlook settings:

either mail.customersdomain.tld or server's hostname

In general, mail.hostname might not exist (it depends...) but simply the hostname should work and should cause no certificate warnings or errors.

If you wish, feel free to PM me the actual domain of your customer and the hostname of your server, and I'll do some remote checks.

 

[Ales]

As you've mentioned in the private message, the outgoing connections in Outlook and iOS seem to be the problem. I took a quick look, trying to connect to various ports and the server's configuration seems OK, except that mail submission is disabled, so there is no response on port 587. This might be the issue, depending on how these clients were configured.

I suggest enabling this feature:

How to enable 587 submission port on Plesk server (Linux)

Apart from that, I see no obvious issues on the server side. If the above does not solve the issue, I suggest inspecting the settings on each of the clients and the networks they are connecting from.

 

[Bitpalast]

The client's IP address could be banned in Fail2Ban. For that reason they cannot connect while others can.

 

[Akrolis]

Hi,

I have a similar issue but with Outlook on the web (not Office 365, just plain outlook.com accounts).

I log in here https://outlook.com with an @outlook.com account and go to Settings->Mail->Sync email->Other email accounts.

I try an account that I already have configured on Thunderbird and Outlook 2010 (desktop) with the exact same settings and Outlook web fails to connect

I tried this with different accounts on different domains on 2 different servers I have with Plesk:
-‪Ubuntu 12.04.5 LTS‬ - Plesk Onyx Version 17.0.17 Update #63
-Debian 9.11‬ - Plesk Onyx Version 17.8.11 Update #69

This is the mail log output when outlook web is trying the configuration:
connect from unknown[52.97.175.53]
lost connection after STARTTLS from unknown[52.97.175.53]
disconnect from unknown[52.97.175.53]

Any desktop mail software I tried works ok (webmail too). It's the outlook.com mail sync with external accounts that fails. Could be just an outlook.com issue?