> On Dec 12, 2018, at 2:49 PM, Selcuk Yazar <selcuk.ya...@gmail.com> wrote: > > Hi, > Some of our users can receive mail from national academic journal site but a > few can't. when i look the logs, it says; > .. > timeout after END-OF-MESSAGE from rs248.mailgun.us[209.61.151.248] > .. > is it about our server or their server ? > > thanks in advance
You'll need a PCAP capture: http://www.postfix.org/DEBUG_README.html#sniffer which you can analyze with wireshark, tshark, or similar. Often this is indicative of path MTU issues, but the PCAP file should tell all. -- Viktor.
