On one one my email accounts-when send emails on my iPhone 5-get bounceback from mobility administrator: Failed to Add Item : Cannot parse search filter. However this email doesn't show up on PC in same account-just my phone

Hi, whilst accessing an email account on my iPhone 5 - I received a spam email (which I didn't open) that I just deleted. However, off of the same account now - I cannot send emails and when I do - I get a bounceback from "Mobility Administrator: Failed to Add the following item because: Cannot parse search filter."

How do I get rid of it and how do I ensure it's gone?

Cheers

S