Dina Lohan to Michael Lohan -- Congratuf***inglations

Dina Lohan briefly suspended her bitter hatred for her ex-husband Michael Lohan on the day of his new son's birth -- telling him, "Congratulations" ... in the most begrudging tone of voice we've ever heard.

Dina was out in L.A. today following Lindsay's turbulent court date when we asked if she had anything to say to Michael -- hours after his fiancee Kate Major gave birth to their new son Landon in Florida -- and she mustered a weak congrats.

As for the whirlwind cross-country trip last night -- Dina said, "It's been a long day ... I'm exhausted." But she added, "We're moving in a good direction."