On Tue, 2012-06-19 at 15:24 +0100, Dennis Davis wrote: > *Extremely* wild stab in the dark here. Try reducing the MTU on > your mail relay(s) slightly. Say from 1500 to something like 1400 > to 1450.
Very good call. Prior to DATA, most transaction packets are far smaller than the MTU of most links in the chain. Post DATA, for messages where the total data size exceeds 1500 or so bytes, they are likely to be larger. If there's a device inline which is breaking PMTUd, or a poorly configured or maintained firewall (in the case of the NHS that was my experience) then sliding your MTU down might well help. Graeme -- ## List details at https://lists.exim.org/mailman/listinfo/exim-users ## Exim details at http://www.exim.org/ ## Please use the Wiki with this list - http://wiki.exim.org/
