If you getting tonnes of returned mails with your email addresses as the senders of the mails, you are probably a victim of a joe-job.
This is when the spammer actually put your email address as the sender and attempt to send spam. If the receiving mail server detects that the email is spam, it will bounce the mail back to the sender which is your email address.
There is a solution to this issue and it is by specifying a TXT record in your DNS servers (you must own the domain name in order to implement it) with the following entry;
If you a Singnet customer, just add Singnet\'s mail server as allowed mail from server and leave the rest intacted.
v=spf1 a mx include:mail.singnet.com.sg -all
The a means that any A records\' IP addresses stated in your DNS will be allowed, the mx means the MX records\' IP addresses will be allowed.
The -all means all the IP addresses allowed are already listed, any others outside this range are not authorized to send emails for your domain.
A ~all will mean allow to send but mails will tagged as highly suspicious, while a ?all & +all will mean allow to send, not required to enforce though still subjected to the querying mail server policies.
If you are a Starhub or Pacific Internet\'s customer, just replace the text mail.singnet.com.sg with your ISP\'s outgoing mail server.
If you\'re still unsure, you may go to SPF configuration page to get more info.
If your environment has complicating setup, you may wish to refer to OpenSPF site for information on setting the SPF Record Syntax correctly.
SPF will only help to reduce bounced mails but may not eradicate it completely as not all mail servers worldwide use or obey SPF syntax.
SPF is an option to reduce a spammer\'s mail delivery rate enough to discourage them from using your email address as sender\'s address.
With the rapid adoption rates for SPF implementation, incorrectly set SPF record may severely impact your operation, so caution is advised when setting it up.
To check the SPF text of a domain, simply do a NSLOOKUP at command prompt, type set type=TXT then type the domain you would like to check.ext record. If it is set in the domain\'s DNS records, you will see a text field similar to the above.
Following is a simple form to check for Whois information covering IP Block owners.
No error checking is done on entries so you will need to ensure that the input are correct or you will not get correct result.
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