Ok - I understand the point about a delay for roaming users getting 'delay' when they send each mail (in reality this will likely only be a one-time deal as once it's been resolved once it will be cached).

For anyone using Haraka for outbound with roaming users, they should be using the delay_deny plugin and exempting authenticated users and relays from most pre-DATA rejections anyway.

I'm going to commit this; but I'm going to make the default 30 seconds as I think it's a more sane default given that this can then be modified in the configuration files should anyone wish to make it shorter.