On Fri, Jun 12, 2026, at 6:46 PM, Mark Sapiro wrote:
On 6/12/26 3:03 PM, Paul Tomblin via Mailman-users wrote:
Can i append or pre-pend another transport file in the transport_maps listing and put in the entry for this domain that's been bouncing people off my list because of too many simultaneous connections?
I don't know what the transport for this domain would be, but the transport_maps setting can contain any number of lookup tables. See <https://www.postfix.org/postconf.5.html#transport_maps>.
It appears you set up a transport with a lower concurrency limit in master.cf like so: slow_smtp unix - - n - - smtp -o slow_smtp_destination_concurrency_limit=5
Then you put an entry in your transport map like so: example.com slow_smtp:
I believe I had something similar on my previous server, but I discarded it because I wasn't sure how well it would play with this lmtp stuff that Mailman was putting in. But remember how I was getting dozens of people bounced off one of my lists all at once, and most of them were at a particular domain? Yeah, this is the underlying cause. Our biggest local ISP doesn't like it when I've got 3 emails going out, and 30+ people at that domain on all of them.
-- Paul Tomblin