Blacklisted IP addresses cause mail send problems
It is highly likely that your internet IP address is on an RBL Blacklist. Mailservers check these blacklists and if your IP address is there, then your messages may not be delivered.
Your internet IP address is randomly assigned to you each time you connect to the internet. It is assigned from a pool of IP addresses from your ISP, and at any given time you are sharing that IP address with thousands of other users. If one user is reported for sending spam or viruses then that IP address can end up on a blacklist, thereby also blacklisting everyone who is sharing that IP address.
To check if you are on a blacklist:
Go to
www.whatismyip.com to get your IP address.
Then go to
www.mxtoolbox.com and click on BLACKLISTS, then type your IP address here to check if it is blacklisted.
If your IP address is on a blacklist, there is an easy way to fix it and a more difficult way.
The more time-consuming way is to contact your ISP and ask them to remove themselves from the blacklist. Supply them with the IP address.
The easy way to get a clean IP is to power off your modem, wait 5 seconds, then power it on again. This will dynamically assign you with a new IP address. Check whether the new IP address is blacklisted. If it is, you may need to switch your modem on and off until you obtain a clean IP address.
NOTE: If your IP address is listed only with Spamhaus-ZEN PBL, this is actually not a problem as it demonstrates your ISP's compliance with PBL. However, if you are listed with any other blacklists, this is very likely to cause mail delivery issues.
