Simpson and Mayer on Feb. 11
and John Mayer have ended their romance – but perhaps not for good, a source close to Simpson tells PEOPLE.
"They have broken up," says the source. "But they have broken up and gotten back together at least 10 times before."
According to the source, the pair are in constant contact – even as Simpson promotes her film Major Movie Star
at the Cannes Film Festival in France. "They talk to each other at least six times a day. I don't know if this breakup is permanent, but for right now they are broken up."
In fact, the pair have "been emailing and talking to each other," since Simpson went to Cannes, says a Simpson friend. "I'm sure they'll get back together."
As for why the two singers split, a friend of Mayer's says, "John did say that he broke up [with Jessica]. He said that it was because he was just over it."
But the pal says there is no other woman. "He's fine about it, he's not upset – but he's definitely not looking for someone right now."
A source who spoke with Mayer recently says the breakup came as a surprise: "Whenever I've seen them, they've been tight and together. I've never seen them argue or anything."
Still, Mayer didn't appear to be taking the split too hard on Thursday. The rocker stayed out until nearly 4 a.m. partying at New York hotspot Stereo. He sat at a back table in the VIP area where he drank two glasses of Jack Daniels and hung out with friends, according to sources.
Reps for Simpson, 26, and Mayer, 29, refused to comment on their clients' personal lives.
PerezHilton.com first broke the news of the couple's split.
Simpson and Mayer have been gradually more and more open about their relationship after months of playing coy. Asked about Simpson in February, Mayer told Time Out New York
, "I'm having the best time of my life, so if the names don't make sense to people, that's so small to me."
Soon after, though, the pair stepped out in a big way, taking a joint vacation
to Italy in March. And when Mayer's Continuum tour hit Australia
in April, Simpson was frequently by his side, spending down time with her beau on Byron Beach.
While Down Under, the two were prone to public displays of affection. Said a fellow passenger flying in business class with the couple from Sydney to Perth: "They were snuggling together."
And Mayer has earned praise from Simpson's family. Recently, Joe Simpson told PEOPLE, "If Jessica is in love, I love the things she is in love with." And he added: "I want her to be happy."
With reporting by KC Baker, Liza Hamm, Mark Dagostino, Lesley Messer and Jeffrey Slonim