Can't send mail via SMTP OR Webmail. Can receive it....

[gmlack]

Today I've started to get this message when trying to send email via smtp.talktalk.net using SMTP.

5.7.1 <my.email@dsl.pipex.com>: Sender address rejected: You are blocked sending mail

This is happening to two accounts, but not a third.

NOTHING has changed at my end.

So what is going on, and how do I regain my ability to send email?

[gmlack]

I've just tried sending from TT Webmail, and it refuses to send too.

Message could not be sent to the following recipients: ["my.gmail@gmail.com" <my.gmail@gmail.com>] (554 - 554 5.7.1 <my.email@dsl.pipex.com>: Sender address rejected: You are blocked sending mail
)

I'm still receiving email OK on TalkTalk....