I've been scratching my head all morning trying to sort this one out. I've got a couple of users in brazil who send webmail emails using Outlook. Their outlook settings are as follows: Email address - firstname.lastname@example.org Username - email@example.com (with all the other settings as they should be.) The reason the email address and username are different is because the email address I want recipients to see (@1111.com) is one that carries our company name as the domain. I have forwarding set up on this address (@1111.com ---> @2222.com) so that incoming mails still arrive at the webmail address. The username has the domain of the webmail provider. Now, everything worked fine until yesterday, but now they can't send outgoing emails anymore. Incoming still works. When testing the settings in outlook everything passes (finds pop, smtp, etc) but the test email sending fails, giving the error message "Unable to send test message. Please verify the email address". If I then change the 'email address' field setting to the address of the webmail domain (@2222.com) test email sending works. So it seems to me that the webmail provider is now checking that all emails sent via its server carry an email address from their domain. (probably to combat spoofing etc). I have no hope of contacting the provider and trying to sort this out as they are a brazilian company. So my question.... can anyone think of a workaround?