unable to reach smtp server

I have the smtpserver set to 192.168.1.11 port 25 and it is listening. I have sent test mails via a different client. The logs with emclient are:
13:26:47.074|028| eM Client 10.3.1720+b574c3b0cc (MAC)
13:26:47.075|028| Account’s UID is 137b93a7-4133-4086-8da7-41407fd0e885
13:26:47.075|028| AccountBase.ChangeOnlineState : State changed to ONLINE due User
13:26:47.090|021| Exception: MailClient.Accounts.SocketException: Connection failed due to the following reason:
13:26:47.090|021| “No route to host [::ffff:192.168.1.11]:25”
13:26:47.090|021| —> System.Net.Sockets.SocketException (65): No route to host [::ffff:192.168.1.11]:25
13:26:47.090|021| at System.Net.Sockets.Socket.DoConnect(EndPoint endPointSnapshot, SocketAddress socketAddress)
13:26:47.090|021| at System.Net.Sockets.Socket.Connect(EndPoint remoteEP)
13:26:47.090|021| at System.Net.Sockets.Socket.Connect(String host, Int32 port)
13:26:47.090|021| at System.Net.Sockets.TcpClient.Connect(String hostname, Int32 port)
13:26:47.090|021| at System.Net.Sockets.TcpClient…ctor(String hostname, Int32 port)
13:26:47.090|021| at MailClient.Protocols.Smtp.SmtpSendCommand.Connect(WorkerStatus status)
13:26:47.090|021| Exception_EndOfInnerExceptionStack
13:26:47.091|021| at MailClient.Protocols.Smtp.SmtpSendCommand.Connect(WorkerStatus status)
13:26:47.091|021| at MailClient.Protocols.Smtp.SmtpSendCommand.Execute(WorkerStatus status)
13:26:47.091|021| at MailClient.Commands.Command.Process(WorkerStatus status)
13:26:47.091|021| AccountBase.GoOfflineAsync : State changed to OFFLINE due BrokenConnection
13:26:47.091|019| AccountBase.ChangeOnlineState : State changed to OFFLINE due BrokenConnection

Why is there no route to host?

The line
13:26:47.090|021| “No route to host [::ffff:192.168.1.11]:25”
suggests the system is trying to connect to the mail server over IPv6, using an IP6 address that includes the IP4 address. Either the use of IP6 is a mistake, or your client is creating a malformed IP6 address.

Correct, but it is em client that is making the mistake, hence the reason for posting here.

Agreed. But something in the environment is causing it to make that mistake. A couple of things to try whenever debugging mail clients:
1- From the command line of the machine running emClient, try ‘ping machine’, using the same name that emclient is using. Observe what IP address it uses. (this tests name resolution).
2- From that same cmd line,
try ‘telnet machine 25’ and see if it’s possible to connect to that machine on port 25. You should see something like:
Trying 52.15.184.56…
Connected to samui.datamat.net.
Escape character is ‘^]’.
220 samui.th.net ESMTP Postfix (Debian/GNU)
quit
221 2.0.0 Bye
Connection closed by foreign host.
james@bahama:~$
3. If it does connect, type ‘quit’ to sign off politely.

Ping works fine and postfix is running on port 25 as I get back prompt at port 25. I still think that it is emclient

Yes. It looks like emClient is for some reason taking the 192.168.1.x address and trying to interpret it as an IPv6 address.
One might try to work around this by making sure emC gets an unambiguously IPv4 address, say in DNS. Or you could use the IPv6 address of the mail server if it’s set up to use IPv6.

The DNS is giving a IPv4 address only.

I have opened a ticket as this worked in 10.1 but stopped working in 10.3. The response I got from Mark was that it is not possible to do so, even though I have that same setup working in 10.1. I wish that they did not break that functionality.

The log from the 10.1 version is

11:37:33.186|00D| eM Client 10.1.4588+f11e2ab373 (Windows)
11:37:33.192|00D| Account’s UID is 7510c48a-0de2-4bc8-9221-dd064966d2f7
11:37:33.192|00D| AccountBase.ChangeOnlineState : State changed to ONLINE due User
11:37:59.415|019| SMTP S: 220 useful.qualitylabworks.com ESMTP Postfix
11:37:59.431|019| SMTP C: EHLO [IPv6:::ffff:192.168.1.160]
11:37:59.431|019| SMTP S: 250-useful.qualitylabworks.com

Is there a way to revert to the 10.1 version?

@feisal

Is there a way to revert to the 10.1 version?

Yes you can revert & install the older V10.1 via going to the release history page below.

https://www.emclient.com/release-history

First close eM Client and “rename the hidden database folder” to eg: eM Client-Old.

(Windows hidden eM Client database folder)
“Users\yourusername\AppData\Roaming\eM Client”

(Mac Hidden hidden eM Client database folder)
“Users\yourusername\Library\Application Support\eM Client”

Then uninstall eM Client V10 3 and install V10.1. You will then need to setup as new.

Thanks, much appreciated