Email problems with postfix

SYSTEM INFORMATION
OS type and version centos 7 min
Virtualmin version virtualmin 7

my thunderbird client is contacting normally to the email server accept the email username and password but when i am going to send the mail the server is telling cannot contact the postfix server, what is that how can i solve it

thank you

nikos

@nsarantopoulos,

Have you checked server error log?

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everything works fine now with mail thank you
the only problem is that they are delivered as spam
i will see what can i do for that