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 could reorder the set as well, or truncate it to just one address).
When in doubt, I would test it, or try to look into the source code of
the mail client in question, if available. If there is a comprehensive
document of this narrowly specific topic, I am not aware of its
existence, sorry.
Regards,
Daniel Ryšlink
On 13-Sep-21 11:07, 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 the theory (either round-robin, or just the first, or
try first and if fail then try next, possibilities to react if server
is running but only makes garbage responses, etc..), but what
behaviour do the "big" email clients actually perform?
i couldn't find the slightest answer using my google fu, nor does any
email client of interest to me (ms outlook, thunderbird, k-9, whatever
iphone is doing) seem to publish any kind of documentation in that
regard.
could someone suggest me a page to read next or google search word to
try out?
best regards,
Max
