Heyo any mammothians in the house this late at night and want to throw on the sword and shield for me?

Basically a new VPS and migrated all WHM accounts from old vps (mammoth also).

New VPS = no emails sending to external domains from any account.

I have been plugging away for hours on this, finally bit the bullet and contact Cpanel Support.
They basically have checked the VPS firewall etc and everything appears to be fine... my thoughts
CPanel are claiming that the issue lies at the network level - something is blocking outbound port 25.

Left a support message @ mammothsvps.com.au

Cheers guys - You are always pretty awesome with any previous issues so thanks in advance!

Well that certainly was easy. Thank you very much for the response Jim - I have only ever used my original mammothvps which is getting ancient now.

I will just pop this link here as a point of reference.
This has been a nice little kick up the ass reminder to keep up to date with this:

http://www.mammothvps.com.au/news

Thanks again!

Have to add that it's worth mentioning this little nugget of info somewhere a bit more prominent on either the sign up page or order confirmation page. I ran into the same problem a few days ago but discovered it pretty quickly (due to my awesome level of admin skills) but can't imagine how long it would drive others insane trying to troubleshoot.

What I wrote was wrong; existing customers were not filtered like this - just new customers.

But we just realised that customers who already had a VPS and signed up for a new one would have been filtered without getting the welcome email. Woops. I will do a news post and make sure this information is pushed out via Twitter/FB as well. Sorry about that yo!

Yeah cheers trog, you guys got me a beauty with this.