Unfortunately many IP addresses get used for sending spam and this gets that address added to a stop list until the provider clears it.
An address may not be on all blacklists.
Not every recipient address will check if the email is coming from a blacklisted address so just because one person receives your email it doesn't mean that the sending IP address isn't blacklisted.
Any one address will not necessarily be stopped for ever any more than a clean address will always be clean.
Hotel and open WiFi can also be susceptible to this problem for this.
Certain areas of the world are more susceptible to this problem e.g. Middle east, Russia.
IF you experience this problem, you get around this by
- If you don’t have a fixed IP address, restart your router which will get a new IP address.
- If you do have a fixed IP address contact your ISP (internet service provider) as they will need to resolve the problem.
- Subscribing to a VPN (Virtual Private Network).
You can check what your IP address is at http://whatismyipaddress.com/
You can check if that IP is blacklisted at http://whatismyipaddress.com/blacklist-check