TLS handshake

[ciadam]

Hi,

For few days i get information on FortiMail 

TLS handshake

Problem sending the message to the recipient, only after 3 attempts the fortimail server sends

[Stephen_G]

Hello ciadam, 

Thank you for using the Community Forum. I will seek to get you an answer or help. We will reply to this thread with an update as soon as possible. 

Thanks, 

Stephen Gerner

Fortinet Community Team 

[Markus_M]

Hi Adam,

typically this is a certificate related problem. Either your FortiMail or the other server will not trust the other node's certificate.

More technical information:

https://community.fortinet.com/t5/FortiGate/Technical-Tip-TLS-and-the-use-of-Digital-Certificates/ta...

Check whether your FortiMail certificates are expired or otherwise invalidated.

with openssl you can check about the other certificate.

openssl s_client -connect theothermail.server:25

openssl s_client -starttls smtp -connect theothermail.server:25

one of them should give some good output about the servers certificate.

Using that same error message in a search engine of choice, like 403 4.7.0 tls handshake, will give you a bunch of more results.

It does sound like either FortiMail or the other webserver are not supporting the same TLS version.

Best regards,

Markus