I'm posting on behalf of someone :-

They have an HTC Desire, and they periodically get the following message when attempting to send out emails:

Warning - Your outgoing server response: 550-Your IP address is on the XBL blacklist! Sending denied.

The phone provides an IP address, which indeed is blacklisted.


This IP resolves to "unknown" somewhere in Germany. We are situated in the UK, as is our email provider.

I have checked with our provider, and the IP of our mail server is not blacklisted (and does not match the one the phone says).

I should add, I am able to send email perfectly well on my iPhone, using (presumably) the same settings. Our computers are unaffected - it is just the HTC.

Does anyone have any advice, or experienced something similar?

I'm reluctant to de-list the IP as I imagine the problem will keep occurring.

Thanks for any insight.

  • I assume this is a standard SMTP account, and not GMail?
    – liori
    Apr 19, 2011 at 19:17

2 Answers 2


I think that the IP in question is the IP of your mobile device or the NAT router that your carrier uses. De-listing won't help here and would in fact just be counter-productive.

Anyway, if you use SMTP with authentication you should never see this message with an SMTP server that is configured proper. Assuming that anonymous SMTP is not practicable or even possible with Android devices, there is nothing you can do.


You should configure SMTP authentication (login and password) when sending outgoing mail.

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