(Not sure if this should be filed here or in the Email Field queue. Glad to move it over there if it's more appropriate.)
When using the email field type for fields created using the Email Field module a validation error occurs when saving content that causes the value not to be saved.
This looks like it's being caused by the value of the items that are being returned and fed to the validation function. The function expects to get back an item with an 'email' index ($item['email']) and is instead getting an item with a 'value' index ($item['value']) which is causing it to choke.
This only happens when using the email field type, using the default text field type everything goes through fine.
"Notice: Undefined index: email in email_field_validate() (line 32 of /path/to/drupal/sites/all/modules/email/email.module)."