IMAP Integration (Cannot connect to SMTP host:)

IMAP Integration (Cannot connect to SMTP host:)

I have configured IMAP Integration. I received the confirmation email that IMAP configuration was successful and Zoho is successfully picking up messages from my Zoho contacts and flagging them however I cannot send mail to a Lead or contact when viewing their profile.  When I am viewing a lead I select Send Mail on the right hand side of the page.  A new window appears where I can compile the email.  When select to send the email I get a message at the top Could not connect to SMTP host mydomain.com, port ##
 However, I can send mail from mail.zoho.com with no issues from my corporate account that has the exact same configuration.