1 & 1 Internet

[the_duderama]

it's most likely reverse dns issues - aol, hotmail etc all use this to verify the senders ip against the mx record.

[ControlG]

I had similar problems a while ago with my provider and on chasing them up it turned out they'd been put on the blacklist of Google and Hotmail as one of their other customers was sending out spam.

The providers mail server had been blacklisted that meant that any mail going through it was being bounced.

Are you getting any info in the bounce back email?

[Sockpuppet]

Not had any problems here but then again I don't e-mail yahoo, gmail, hotmail etc

[sidknows]

anyone aware of the problems 1& 1 internet are having
they host my domain and apparently anyone use 1 & 1 cannot send emails to hotmail , yahoo , google etc