Check with your email provider what the correct settings are, and use those. They probably do have a support web page. Setting up a new account without SSL/TLS these days doesn't make any sense. If your email provider doesn't support SSL/TLS look for a different provider.

I can use both an insecure server and a secure server at my host. I can successfully create pop accounts on both servers. I cannot create IMAP accounts on either server. According to the host's website the only difference for setup is using a different port. Thunderbird correctly identifies the correct ports for both the Pop and IMAP servers. But it cannot create a Thunderbird account when using IMAP.

When using the secure server it uses TLS. I thought I'd reduce variables by trying to create the IMAP account using the insecure server. When I try to set up an imap account using the secure serve (autodetect comes back with STARTTLS) I don't get the warning about security, but when I click "done" it checks the password again for a long time, and then eventually reports back the same error about the name or password being invalid. That is, same behavior.

I can use both an insecure server and a secure server at my host.

As said before, as long as 'a secure server' is offered by the email provider there is no point trying the 'insecure server'. I'm not sure what 'at my host' means.

I can successfully create pop accounts on both servers.

Since you're trying to set up in IMAP account I guess POP is irrelevant.

According to the host's website the only difference for setup is using a different port.

What are the exact settings for IMAP as per your provider's information?

when I click "done" it checks the password again for a long time, and then eventually reports back the same error about the name or password being invalid.

Have you checked with your provider about the error?

Let me be as specific and as clear as possible, since this seems to be a Thunderbird issue.

Image 1 is the instructions from the e-mail host. You will see the host names and ports for both pop/imap and stmp, both for standard and secure.

Image 2 is starting the Thunderbird account setup. After continue, I select manual configuration.

Image 3 shows the setup in manual configuration after I insert the server names for the secure host, using imap. I then click re-test.

Image 4 shows the result, which comes back in less than 10 seconds. It shows the correct ports and security settings for imap. I then click done.

Thunderbird then retests, rather than setting up the accounts. Image 5 shows what is displayed for 6:30 minutes.

After 6:30 minutes, Thunderbird reports that there is a problem, as shown in image 6.

If I change the incoming from imap to pop, I can click retest and it reports similar to image 4 but with port 110 for incoming, which as shown in image 1 is the correct port.

I can then click done, and the pop incoming and smtp outgoing accounts are setup without further retesting.

Is this now clear?

your settings say your user name is testrob@scruffyraven.com.

The settings page you posted from Thunderbird shows your user name as testrob.

My guess is there is an error in the user name. hence no work.

That is how Thunderbird filled it in. It works successfully with these usernames if I do pop instead of imap. However, I'll try specifying the username as testrob@scruffyraven.com instead of just testrob and see if that lets the imap account creation be successful. I'll report back tomorrow. Thanks.

Well, it was worth a try.

As suggested, I filled in the entire username, including the part starting with @, rather than keeping the part before the @ that Thunderbird filled in.

Image 1 shows the setup before clicking re-test. All looks good.

Image 2 shows the result after clicking re-test. The autodetect identified the correct ports and SSL. All looks good (and the same as before).

After clicking done, setup went back to retesting the configuration. The good news is that it took only 4:30 instead of 6:30 to come back with image 3 which says the configuration could not be verified and suggests the username or password is wrong. That is, same result.

Because I can set up the account without a problem if I set it up as a pop account but cannot successfully set it up if it is a imap account, this suggests to me a problem with Thunderbird.

I have contacted the email host (omnis.com) and they confirm the only differences in settings between pop and imap is choosing imap and port 143.

what ISP and internet modem do you have? I have seen issues with older comcast modems, they blocked the ports way back and then actually decided to use them themselves.. It may be port 143 is blocked in the firewall on the modem thus killing off results.

There's one more thing you can try. IMAP: port 993, SSL/TLS instead of STARTTLS SMTP: port 465, SSL/TLS instead of STARTTLS

Success, eventually.

I checked port 143. It is open. See the Kaspersky report of ports that shows that 143 is active.

I tried IMAP: port 993, SSL/TLS instead of STARTTLS SMTP: port 465, SSL/TLS instead of STARTTLS. This resulted in failure. See image 2.

I tried IMAP: port 993, SSL/TLS and left the stmp on autodetect. It came back with port 587, starttls. See image 3.

When I clicked done, it created the account. I have been able to send emails to and from this account.

Note under the port report that 993 is listed as imap ssl. Oddly, port 587 isn't even listed. Also oddly, while port 587 is the smtp port specified by the email host, the email host specifies port 143 for imap and doesn't mention port 993. Whatever. If it works, great.

Thank you all for your suggestions. I hope this effort can help others. It was frustrating, but seems to be working now.

Port 143 is the standard for unsecured IMAP. Port 993 is the standard for secured IMAP (SSL) Port 587 is the standard for SMTP (client transmission) Port 465 was set aside for secure SMTP (client transmission using SSL) but never ratified as a standard, it is however sometimes used by server administrators for that purpose Port 25 was the original transmission port client to server and server to server. The client use was branched off to port 587 in 1998 leaving port 25 for server to server transmission.