As the documentation says, the success object is returned from the sendmail subroutine.

if (sendmail($email)) {
    # On success
}
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Without success, the subroutine thows an exception, i.e. dies. Therefore, without evaling the subroutine (or using something like Try::Tiny), you don't have to check the success.

if (eval { sendmail($email) }) {
    # On success...
} else {
    # On failure
}
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