Outgoing mail on iPhone

I'm having a problem sending mail from my iPhone through Apple Mail. I am using my own domain, and noticed on my computer that for the outgoing SMTP, I had to use smtp.zoho.com:myemailaddress in order for outgoing mail to be sent out. When I try to do the same on my iPhone, it seems to default to smtp.zoho.com even when I type in the : followed by my email address. I think I have followed the instructions on the help page, and it isn't working. Help!