Magento transactional emails somehow get additional escape characters added to the headers.
Magic_quotes are disabled in PHP.
Postfix uses Elastic Email as a relay. According to Elastic, e-mail are received correctly.
Then majority of clients receive the emails correctly, except those who are behind messagelabs.com filter. After reviewing the logs, the messages are rejected by messagelabs.com because additional slashes are added to the emails.
Has anyone ever come across this issue? Which piece could be at fault? Again, majority of customers receive emails perfectly fine.