Norbert,
Just sent you a direct message. It was delivered to you from
ironport-c300vb.dcptech.com
23 Oct 2025 08:05:39 (GMT -04:00) SMTP delivery connection (DCID
590422) opened from Cisco IronPort interface
2620:ee:8000:101:0:a:196a:c0df to IP address 2a00:0:2d41:2:178:15:145:70
on port 25.
23 Oct 2025 08:05:40 (GMT -04:00) Delivery connection (DCID 590422)
successfully accepted TLS protocol TLSv1.2 cipher
ECDHE-ECDSA-AES256-GCM-SHA384 None.
23 Oct 2025 08:05:45 (GMT -04:00) Message 210610 to
[email protected] received remote SMTP response '2.6.0
<[email protected]>
[InternalId=26474178412560, Hostname=edge02.systema-online.de] 7144
bytes in 4.764, 1,464 KB/sec Queued mail for delivery'.
David
--
https://dprall.net
On 10/23/2025 5:37 AM, Fehlauer, Norbert via mailop wrote:
Hi,
I'm experiencing delivery problems from senders which uses Cisco ESA systems to
our on-prem Exchange systems. It seems that TLS negotiation fails between
sender and our system.
Error: TLS negotiation failed with error AlgorithmMismatch
As I did not change anything on my side regarding the used ciphers, it seems
possible that Cisco rolled out some change to outbound TLS security. As I do
not have access to an ESA, can anyone comment if my assumption is correct?
And maybe if this is the root cause can give me a hint what I can tell the
sender admins? I guess somewhere at Cisco there would be some kind of
documentation about the current default ciphers.
Kind regards
Norbert
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