Sending mails with smtp of my ISP

[budwaiser]

Hi,
i use Outlook to send mails with smtp of my ISP.

Sometimes happens that i have problems to send mails with this configuration and i have noticed that, using smtp of my account (mail.mydomain.com) i have no problems anymore.

My question is:

is it dangerous use smtp of the server? (mail.mydomain.com)

Why usually i should use smtp of my ISP?

Thank you

 

[budwaiser]

Thanks for your help