Check your IP address against block lists.
Sometimes you may experience problems sending or receiving mail because the IP address that your ISP has given you is listed in spamming block lists. This isn't your fault, and if you are listed, just disconnect from the internet (eg, turn off your ADSL router or your mobile phone), leave it five minutes and reconnect. You should then be allocated a new IP address.

You can use the tools below to check if your IP is listed as a sender of spam.

All of these links open a new window.

Check at Spamcop
A great list that catches out a lot of spammers - very reliable!

Check at Spamhaus
We use their Zen list which is a combination of all the Spamhaus lists.

Check against every list
DNSBL have a great site that checks every blocklist around the world.