You may choose to use the SMTP Server of your local Internet Service Provider (ISP) for sending Emails. Here are some reasons why:
If you are using any SMTP server than our Email server, an important change must be made in your hosting control panel. This is because our system uses the Sender Policy Framework
(SPF) that by default designates our Email server as the only authorized server
for sending Email from your domain.
In other words, if you use a third party (your ISP's) SMTP server, your Emails may be rejected by the recipient since it originated from a server that is not authorized (by SPF) to send Emails for your domain name.
To avoid this issue, add your ISP's SMTP server to the SPF record as authorized to send email for your domain.
First, you need to know the IP Address or Host name of the SMTP Server you would like to use.
SPF records are DNS records, and DNS records may be cached by other DNS servers, so the changes you make may take some time to propagate across the Internet.
Here is the syntax reference for SPF records: http://www.openspf.org/SPF_Record_Syntax