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Sonicwall TZ300 Blocking Outbound SMTP

Our tz300 is suddenly blocking outbound smtp port for 25, 587 and 465. Default config and policies are setup and nothing has changed with the Sonicwall or the ISP connection. I’m certain that the default behavior is for all outbound ports to be open. As a test, I have disabled all security features. Kinda stumped by why these smtp ports are no longer connecting, which is preventing Outlook from sending emails. If I connect directly to the ISP device, I am able to use smtp, so I’m certain the Sonicwall is blocking outbound smtp traffic.

Any suggestions or advice is appreciated.

Category: Entry Level Firewalls


  • Options
    AjishlalAjishlal Community Legend ✭✭✭✭✭


    Assume you are using POP3 account to send emails. Most probably your email hosting provider blocked your office public IP due to multiple login issue.

    If you have any logs you can share with us for analyzing.

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