Re: multiple ip addresses for submission -- My Google Fu is lacking

2021-09-14 Thread raf
On Tue, Sep 14, 2021 at 08:24:00AM +0100, Nick Howitt wrote: > On 14/09/2021 04:29, raf wrote: > > > > On Tue, Sep 14, 2021 at 01:20:03PM +1000, raf wrote: > > > > > > > But chances are that mail clients just do what any > > other TCP client would do. That might be why you can't > > find

Re: multiple ip addresses for submission -- My Google Fu is lacking

2021-09-14 Thread Gerald Galster
> when a user clicks "send", the email client has to make some tcp-connection > to some ip address. > what if the hostname configured at the email client resolves to multiple ip > addresses? There are several hops that could randomize ips: - authoritative dns server - dns resolver at your

Re: multiple ip addresses for submission -- My Google Fu is lacking

2021-09-14 Thread Max-Julian Pogner
If you are only interested in what mail clients do, and can't find any online explanation, you could either look at the source code to some open source ones (probably the easiest way), to me, this feels rather the most troublesome way :-) or set up a mail smarthost with multiple IP

Re: multiple ip addresses for submission -- My Google Fu is lacking

2021-09-14 Thread Nick Howitt
On 14/09/2021 04:29, raf wrote: On Tue, Sep 14, 2021 at 01:20:03PM +1000, raf wrote: But chances are that mail clients just do what any other TCP client would do. That might be why you can't find any discussion on the topic. Remember, the only IP address(es) that the mail client will be

Re: multiple ip addresses for submission -- My Google Fu is lacking

2021-09-13 Thread raf
On Tue, Sep 14, 2021 at 01:20:03PM +1000, raf wrote: > On Mon, Sep 13, 2021 at 11:07:27AM +0200, Max-Julian Pogner > wrote: > > > Hi there, > > > > when a user clicks "send", the email client has to make some tcp-connection > > to some ip address. > > what if the hostname configured at the

Re: multiple ip addresses for submission -- My Google Fu is lacking

2021-09-13 Thread raf
On Mon, Sep 13, 2021 at 11:07:27AM +0200, Max-Julian Pogner wrote: > Hi there, > > when a user clicks "send", the email client has to make some tcp-connection > to some ip address. > what if the hostname configured at the email client resolves to multiple ip > addresses? > > i actually know

Re: multiple ip addresses for submission -- My Google Fu is lacking

2021-09-13 Thread Viktor Dukhovni
On Mon, Sep 13, 2021 at 07:58:26AM -0400, Wietse Venema wrote: > > When a user clicks "send", the email client has to make some > > tcp-connection to some ip address. What if the hostname configured > > at the email client resolves to multiple ip addresses? > > It just seems unlikely that major

Re: multiple ip addresses for submission -- My Google Fu is lacking

2021-09-13 Thread Wietse Venema
Max-Julian Pogner: > Hi there, > > when a user clicks "send", the email client has to make some > tcp-connection to some ip address. > what if the hostname configured at the email client resolves to multiple > ip addresses? It just seems unlikely that major email service providers would run

Re: multiple ip addresses for submission -- My Google Fu is lacking

2021-09-13 Thread Daniel Ryšlink
I would hazard a guess that the client connects to the first IP from the RRset his cashing DNS resolver gives him (since mail clients AFAIK do not have in-built DNS resolver functionality. How is the resource record set ordered depends on setting on the server, usually (though the DNS client

multiple ip addresses for submission -- My Google Fu is lacking

2021-09-13 Thread Max-Julian Pogner
Hi there, when a user clicks "send", the email client has to make some tcp-connection to some ip address. what if the hostname configured at the email client resolves to multiple ip addresses? i actually know the theory (either round-robin, or just the first, or try first and if fail then