hikerlive said

1.Thunderbird version: thunderbird v68.1.1, operation system: macOSX high sierra 10.13.6 2.Some days ago i can get mail messages, but now can not, like as " could not connect to server mail.butel.com; the connection was refuesed." 3.I attempt to remove account and add again, result "component returned failed code: 0x8000fff(NS_ERROR_UNEXPECTED)", attempt thunderbird v60.9.4, v52.9.1, that can not add mail account. 4.Additional: a) my email server work normal, such as foxmail can add mail account successed. b) windows thunderbird v60.9.4 add the same mail account successed. So I judge that some setting affect the thunderbird.

Check to be sure your username and password are still good by logging into your webmail account through http://butel.com/

And, Yes, there is an Error in the log that TB couldn't find your account settings. Try going to the tools menu and clicking on "Account Settings".

Look at the entry for your butel.com/ mail account and check the server settings under it. Maybe when you click "OK" it will write the settings again into the preferences and that error will go away.

Can you update to the latest TB? I'm using TB 68.1.1 On Sierra OS ....

@ See Mac: 1、Butel email server setting is ok, i check many times, and change the computer to use thunderbird, result is same. ok.

2、I use wireshark tool to catch network ip package, found that no any data transfer to mail server, like maxOSX forbid thunderbird to access network, but I check system firewall setting, no forbid. so no idea and I stop here.

When I add mail account and click re-test button , i open the thunderbird error console. The error message is:

• 2019-10-11 18:14:35 mail.setup INFO manual config to test:
• Incoming: pop3, mail.butel.com:110, no SSL, auth: plain, username: (redacted)@butel.com, password: set
• Outgoing: smtp, mail.butel.com:41000, no SSL, auth: plain, username: (redacted)@butel.com, password: set
• 2019-10-11 18:14:35 mail.setup WARN spinner start looking_up_settings_halfmanual
• 2019-10-11 18:14:35 mail.setup INFO status msg: Looking up configuration: Probing server
• 2019-10-11 18:14:35 mail.setup INFO switching to UI mode manual-edit-testing
• 2019-10-11 18:14:35 mail.setup INFO progress callback host mail.butel.com port 110 type pop3
• 2019-10-11 18:14:35 mail.setup INFO progress callback host mail.butel.com port 41000 type smtp

• TypeError: NetworkError when attempting to fetch resource. 2
• 2019-10-11 18:14:35 mail.setup INFO progress callback host mail.butel.com port 110 type pop3
• 2019-10-11 18:14:35 mail.setup INFO guessConfig failed: Can't find a server
• 2019-10-11 18:14:35 mail.setup WARN status error failed_to_find_settings
• 2019-10-11 18:14:35 mail.setup INFO status msg: Thunderbird failed to find the settings for your email account.
• 2019-10-11 18:14:35 mail.setup INFO switching to UI mode manual-edit-have-hostname

The key error message: TypeError: NetworkError when attempting to fetch resource. 2

I see two seriously odd things in this setup.

1. I have never seen SMTP configured on port 41,000. Try configuring your mail server to use a low port, perhaps even one of the "standard ones" but certainly less that 1,000. There be dragons above 1,000 because they are largely unused for anything. although 40,00 to 41000 can be used by some FTP installations. But is usually a UDP port.

2. Errors such as your last image normally shows the server name. That it is returning "self hosted" makes me wonder exactly what is happening there.

But I would guess that it is the port number that is causing the issue. Why it is I am not so sure. It might even be a regression caused by https://bugzilla.mozilla.org/show_bug.cgi?id=1500105

So some questions, that I may understand better your setup..

Is the server mail.butel.com an exchange server? If it were on the "local network" it might explain the "self hosted", and some other things.

If you use the command prompt and type tracert mail.butel.com and tracert self-hosted do they both resolve to the same IP address. does self-hosted resolve at all?

Thanks all, I find the problem reason, It is thunderbird network used proxy setting, and change it no proxy.

That can explain below error message: 1、could not connect to server mail.butel.com; the connection was refuesed.

2、"TypeError: NetworkError when attempting to fetch resource."