Warmed, Dedicated IP - Discontinuing Relay - Rewarm?

[Richard_Thomsen]

My organization implemented Marketo last year.  We have the Dedicated IP feature but also ended up delivering email through a corporate email relay (Marketo>Corporate email relay>Internet).  While they did several months of 'IP Warming', we are now planning to disconnect from the corporate email relay (email directly from Marketo).  Is IP Warming required again if our Dedicated IP is unchanged?

I am asking about this because I wonder if the purpose of the warming is more for the last hop prior to delivery (which would have been our corporate email relay).  Now that the messages will deliver directly from Marketo, I'm uncertain if we are still OK or need to warm all over again.  

[SanfordWhiteman · Accepted solution]

You absolutely need to warm the IP, because remote MXs have never seen that IP before. (Note any IP in a Received: header can be forged, so there'd be no reason to trust it just because it appeared to be in the chain.)