Who is your mail provider? What setting values have you tried?

Hi

Mail provider is Nexcess.net

For incoming:

 Hostname: my-hostname
 username:  my-username
 protocol: IMAP
 port: 993
 Connection: SSL/TLS
 Authentication: Normal Password

For Outgoing:

  Hostname: my-hostname
 username:  my-username
 port: 587
 Connection: STARTTLS
 Authentication: Normal Password

I've used different combination of these values suggested by provider support team but nothing worked.

RE: 'Server name' Apparently you should have received the Nexcess mail server information provided in your Nexcess Welcome Email. Info at link includes this: If you use a shared or dedicated server, use the server’s hostname; for example: cloudhost-123456789.us-midwest-1.nxcli.net sip1-123.nexcess.net or obp1-01.nexcess.net. Do not use any other domain that has a DNS record that points at the mail server or your domain; for example, mail.example.com.

If you use a server cluster, Nexcess recommends using the DNS instead of the server’s hostname for the sake of simplicity. If you prefer to use the server’s hostname, contact the Nexcess Support Team for assistance.

Info located : https://www.nexcess.net/help/how-to-configure-your-local-email-client/

https://www.nexcess.net/help/configuring-different-email-clients-with-nexcess-email-accounts/

Username = full email address Password - this is the same password you would use to access that email address webmail account.

Hi

I'm doing exactly mentioned in the ref link. I'm using "my-username" and " my-hostname" in my last response just for privacy concern. I thought it should not be pasted here openly.