mail undelivered

[norfolkbird]

I suddenly starting having my mail undelivered....or getting the URL secuirty image before being allowed to send mail..
this is only on one email address but to all contacts..encluding work..
whereas on my other address its just my work address that is reurned undelivered.
I have dont nothing differently...

any help please

IN IDIOTS language as I am not very pc literate
thanks

[norfolkbird]

ps excuse typo's

[rojash]

Please excuse typo's apostrophe?