Re: [Astlinux-users] Cannot send mail from Astlinux

[Lonnie A. <li...@lo...>]

> On Mar 26, 2020, at 4:31 PM, Michael Knill <mic...@ip...> wrote:
> 
> Hi Group
>  
> I have a site that I cannot send mail from yet it is configured exactly the same, with the same Astlinux version as many others that are working to the same mail server (Office 365).
> I get ‘msmtp: the server does not support TLS via the STARTTLS command msmtp: could not send mail (account default from /etc/msmtprc)‘
>  
> Now it is sitting behind a firewall with a bit of intelligence (or not) so I'm wondering if it is blocking something related to the TLS setup.
>  
> Any ideas? 

I suppose an SMTP ALG in the firewall could be causing issues.

Recall that encrypted mail can be sent via STARTTLS or TLS/SSL.  TLS/SSL (typically port 465) is fully encrypted before any data is exchanged.  STARTTLS starts out using plain text until STARTTLS  is negotiated and switched to an encrypted connection.

A SMTP ALG could make the STARTTLS not operate properly since it starts out as plain text.

If you can, use TLS/SSL so the connection is fully encrypted.

Lonnie