Scenario:

Is my ISP (Internet Service Provider) isn't blocking port 25 but I can't connect to MX Outbound?

Solution:

Your ISP isn't blocking, filtering or redirecting SMTP TCP Port 25, but you still can't connect to a MX Outbound server.

The are a number of things to try

1. Check your own firewall settings on router and ensure you have no restrictions/rules turned on that could prevent emailing
   
   
2. Check your own firewall settings on the PC and ensure you have no restrictions/rules turned on that could prevent emailing
   
   
3. Try disabling your anti-virus software.   Some AV's capture and redirect port 25 to itself in order to scan outbound emails.  Sometimes this can cause problems when sending emails.  If this is the case try a different port (see alternative ports for MX Outbound) or disable the outbound scanning.