Email error can’t send email invalid

[MARKBIDWELL]

I’m trying to send emails on my iPhone i keep getting error messages “can’t send invalid emails address. I can’t reply to emails I’ve received. Very annoying ##

[BasilDV]

Hi @MARKBIDWELL 

Are you using your TPG email account? 

If yes, have you tried responding via Webmail (Post Office)?

Was it working fine before?

BasilDV