According to reports, the 48-year-old Justice League actor began penning his ex-fiancée romantic emails in February while J Lo was still engaged to the former Yankee.
The emails reportedly started out innocent enough but allegedly escalated with both parties.
Fans will recall, J Lo was filming Shotgun Wedding in the Dominican Republic during that time and rumors were swirling about a breakup with A-Rod.
But the then-couple seemingly put those split rumors to bed when A-Rod flew over and planted a sloppy kiss on the singer right in front of photographers.
It's now reported that Affleck was communicating with J Lo during that time and it got flirty.
Sources tell TMZ the actor began reaching out via email after he saw photos of his ex filming in the D.R.
FYI -- J Lo played a bride who wed Josh Duhamel so there were lots of pictures of her in a wedding gown.
According to the outlet, Affleck reached out and told his ex-fiancée how beautiful she looked and how he desired to be in the Caribbean with her.
Sources allegedly said the flirty exchange wasn't a one-way street.
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J Lo reportedly also expressed her love for Affleck's writing and said he was able to "own her heart" with his words.
The outlet also reports they continued emailing each other until she got back to Los Angeles, where Affleck was caught by paparazzi leaving her home.
They also allege there was no physical contact between the two while she was in the D.R.
A-Rod and J Lo ended their two-year engagement in April.
Later that month, Affleck was seen leaving her L.A. home, sparking a Bennifer 2.0 firestorm.
J Lo and Affleck were photographed together for the first time over the weekend during a snowy trip to Montana.
Sources tell RadarOnline.com that J Lo is just "testing the waters" and has major reservations due to Affleck's dating video that went viral last week.
"He’s a good man and a good friend, but not husband material,” our insider said, adding, "She’s still angry with Alex [Rodriguez] and might have wanted revenge."
The source also said that the video of Ben "creeping around a much younger lady" isn't helping matters, pointing out that her relationship ended with A-Rod after the scandal with Madison LeCroy.