If I set up my iPhone to use ActiveSync (so I can have push notifications), when I send a message, my custom SMTP settings are not honored.
I have added a custom from address and SMTP server to "Send mail as", and set this as my default from address.
When I send an email using Zoho Webmail, it correctly uses my custom SMTP server as a smart host. However, when I send an email using my iPhone with ActiveSync (EAS) connection to Zoho, it does not use the custom SMTP server as a smart host, it sends the message directly from Zoho servers.
This causes SPF to fail since it is not using the smart host!