An unsolicited manuscript is basically a manuscript that hasn't been asked for. In other words, it is an uninvited manuscript. There are many publishers and agents who do not accept unsolicited material.
The reason for this is because agents and publishers receive dozens of samples each week, and so they request that authors do not send unsolicited material so that they are not swamped.
An enquiry letter would be the best way to approach an agent who does not accept unsolicited material, or perhaps a phone call. This saves hassle for both the agent and the author, as the agent won't have to look through a manuscript that hasn't been asked for and the author doesn't have to waste their time compiling the manuscript to be sent off.
There are agents who do accept unsolicited material, asking for authors to submit samples with a covering letter and a synopsis.
The reason for this is because agents and publishers receive dozens of samples each week, and so they request that authors do not send unsolicited material so that they are not swamped.
An enquiry letter would be the best way to approach an agent who does not accept unsolicited material, or perhaps a phone call. This saves hassle for both the agent and the author, as the agent won't have to look through a manuscript that hasn't been asked for and the author doesn't have to waste their time compiling the manuscript to be sent off.
There are agents who do accept unsolicited material, asking for authors to submit samples with a covering letter and a synopsis.