IP has poor reputation

[#1]

Hi,
I use authenticated SMTP to send e-mail from my phone and also for a "Contact Me" page online.  I have noticed in the last couple of weeks that the web server's IP has been blacklisted by Plusnet and gives the error "535 authentication rejected as IP has a poor reputation".  Well, maybe it does, but I don't believe it's a poor reputation from my site, probably some oik on the shared server has done something naughty and presumably Plusnet uses a shared blacklist.
What is more annoying is this morning my phone wouldn't send an e-mail.  Same error message. IP address x.x.165.237.  Reboot phone and get a new IP x.x.164.65 and it works ok.  Therefore I'm being blacklisted if I'm getting a dynamic IP which has (in Plusnet's view) been naughty in the past.
What can I do (other than change ISP) to stop this random blocking of my outgoing e-mail?  Seems pretty pointless to have some IPs blocked from my phone provider but not others!

[#2]

Quote

What can I do (other than change ISP) to stop this random blocking of my outgoing e-mail?  Seems pretty pointless to have some IPs blocked from my phone provider but not others!

PlsuNet use the Cloudmark system to control spam so if they are blocking some IPs then other ISP's are likely to be blocking them as well. You could try sending email via your mobile providers smtp server as they are more likely to try and keep that off any blackists

[#3]

The problem with that is when I use my tablet or laptop out and about, that's fine, but when I'm at home the SMTP settings will be for my phone provider.
Maybe I am naive, but I'd have thought it was quite unlikely that if I was a spammer, I'd log into an authenticated SMTP server and send an e-mail to one or two recipients and then not send anything for a bit, then send another small e-mail a while later.  It seems the decision is being made entirely on "he's sending e-mail from a dynamic IP address that sent suspected spam some time ago" rather than a proper risk assessment based on IP, recipients and content.
jim:quote