We us a custom SMTP server from Sendgrid.com with our Google Apps account. When editing the account in eM client it lets me update the SMTP server, but I cannot find where to enter the separate login credentials for it. Am I missing something or is this not possible with eM client?
It is unfortunately not possible to set a separate SMTP for e-mail accounts in eM Client. What you could do is to set the SMTP up as another account through the new account set up and disable the SMTP service for the google app account (in the general tab in Menu -> Tools ->Accounts of the relevant account).