Header names should follow rules described here:

https://tools.ietf.org/html/rfc5322#section-2.2

However, rules for custom headers seems to be more restrictive - for example @ or = are not allowed.

I see that these characters are mentioned in https://tools.ietf.org/html/rfc2616#page-16, but it only says that they should be in quotes. However I am not able to configure header containing them in quotes either.

Is this on purpose?
If yes, this needs to be mentioned in analysis&documentation. If not, we need to create critical JBEAP jira for 7.4