Monday, 29 June update - this is an intermittent problem. Please report any issue you are having emailing to mailing lists so we can provide a fix as soon as possible.
We are experiencing problems with users who are trying to send email to centrally managed mailing lists (for example @buildings, @courses etc.). We are urgently working to resolve this problem but in the meantime there is a workaround and your local IT Supporter team will be able to assist those who need to send emails to this particular type of list.
We apologise for the inconvenience caused.