On Wed, Aug 28, 2013 at 9:35 AM, Michael Richter <MRichter@sasag.ch> wrote:

mrichter@CL-LINUX-3OG-MR:~$ telnet mxzhh.bluewin.ch 25
Trying 195.186.227.50...
Connected to mxzhh.bluewin.ch.
Escape character is '^]'.
421 4.4.5 Service unavailable, concurrency limit reached.
Connection closed by foreign host.

Trying 195.186.227.50...
telnet: connect to address 195.186.227.50: Connection refused
telnet: Unable to connect to remote host

This with all 3 MX:

bluewin.ch.        88    IN    MX    10 mxbw.bluewin.ch.
bluewin.ch.        88    IN    MX    42 mxzhb.bluewin.ch.
bluewin.ch.        88    IN    MX    42 mxzhh.bluewin.ch.

I just wanted to verify this and the very first time it worked:

# telnet mxzhh.bluewin.ch 25
Trying 195.186.227.50...
Connected to mxzhh.bluewin.ch.
Escape character is '^]'.
220 zhhdzmsp-mxin28.bluewin.ch ESMTP Service (Swisscom Schweiz AG) ready

But right after I got the same error as you:

# telnet mxzhh.bluewin.ch 25
Trying 195.186.227.50...
Connected to mxzhh.bluewin.ch.
Escape character is '^]'.
421 4.4.5 Service unavailable, concurrency limit reached.
Connection closed by foreign host.

But then again...

# telnet mxbw.bluewin.ch 25
Trying 195.186.99.50...
Connected to mxbw.bluewin.ch.
Escape character is '^]'.
220 zhbdzmsp-mxin15.bluewin.ch ESMTP Service (Swisscom Schweiz AG) ready

# telnet mxbw.bluewin.ch 25
Trying 195.186.99.50...
telnet: Unable to connect to remote host: Connection refused

# telnet mxzhb.bluewin.ch 25
Trying 195.186.99.50...
Connected to mxzhb.bluewin.ch.
Escape character is '^]'.
220 zhbdzmsp-mxin19.bluewin.ch ESMTP Service (Swisscom Schweiz AG) ready

Seem to be very "random" problems:
- 421 4.4.5 Service unavailable, concurrency limit reached.
- Unable to connect to remote host: Connection refused

- Sometimes connection works fine