T-Pain, who laced the first single, is only one of the many featured guests throughout the album. Timbaland, who produced the second single "Elevator", is also featured on the track. Rick Ross, and Trey Songz made appearances as well.Lil Wayne has also been added to the list with assistance by young Memphian, Jamil Smith, while Sean Kingston appears on the J. R. Rotem-produced "Roll" the concept was created, and co-written by Compton rapper Spitfiya, from The Bullets Production Team, Various other guests include Birdman, Brisco. The third single is "In the Ayer" featuring will.i.am. The fourth single was scheduled to be "Money Right" featuring Brisco, and Rick Ross, but was canceled due to the release of his upcoming second studio album R.O.O.T.S. His second collaboration with T-Pain, "I Bet", as well as his collaboration with Trina, named "Bout It", both didn't make the final track list, but were recorded. As for production, J. R. Rotem, DJ Montay, and Timbaland all provided tracks for Mail on Sunday, among others.
Mail on Sunday garnered mixed reviews from music critics. At Metacritic, which assigns a normalized rating out of 100 to reviews from mainstream critics, the album received an average score of 54, based on 12 reviews.
Steve 'Flash' Juon of RapReviews praised the album for containing great production and tracks that are potential singles but found the artist on said album lacking in identity, concluding with, "When you try to come up with positive comparisons to other artists, you realize just how derivative Flo Rida is. He's a little bit Twista, a little bit Trick Daddy, and a whole lot Nelly. None of those things are negative, but the fact he can't distinguish himself from any of them isn't a positive. I'd like to see Flo Rida convince me why he's special with his next album - until then he's just another MC with a well produced album who came out of a cookie cutter hitmaking mold." Joseph Barracato of Entertainment Weekly also praised the production for having "ferocious beats" and "infectious hooks" but gave credit to Flo Rida for delivering female anatomy metaphors in a creative way.Billboard writer Jeff Vrabel said that, "Flo Rida's flow is an engaging/ringy-dingy/he-sounds-like-Nelly thing. But his hooks can be rock-solid ("Ack Like You Know") and his interest in gleaming synthesizerism (opener "American Superstar" comes into "Tubular Bells" territory, really) helps set him off from the legions of rappers clawing over each other to break out of the South."
AllMusic's Andy Kellman said that, "Though Flo Rida has his own identity – for all the tough talk and the automotives fixation, he does come off as big-hearted, and he could just as easily make an R&B album – and covers more bases than what is typical from other mainstream-yet-street rap albums of 2007 and 2008, he's not nearly as distinctive as any of his predecessors."Robert Christgau graded the album as a "dud", indicating "a bad record whose details rarely merit further thought."Rolling Stone's Christian Hoard found the album trying hard to replicate the success of "Low" but found the tracks to be "generic pop rap" and both the production and vocal delivery "standard-issue." Wilson McBee of Slant Magazine criticized the record's tired use of party tracks, phoned in contributions, and misogynistic lyrical content, concluding that "unless he can once again catch the coattails of T-Pain or some other hit-magnet, odds are that he’ll be beginning his descent back into anonymity very soon."
Mail on Sunday debuted at number four on the US Billboard 200 chart, selling 86,000 copies in its first week. As of May, 2009, the album has sold 390,000 copies in the US. It has been certified silver for sales in the UK.