Backup not complete (IMAP server returns multiple responses for search)

[skilltryck]

Just installed and tried a local backup for my imap-account.
Resulted in 700+ emails only being 9 locally.

After debugging with double --verbose I identified that UID SEARCH ALL returns multiple responses and only the last one is handled.

S: * SEARCH 1707 1708 1709 1710 1711 1712 1713 1714 1715 1716 1717 1718 1719 1720 1721 1722 1723 1724 1725 1726 1727 1728 1729 1730 1731 1732 1733 1734 1735 1736 1737 1738 1739 1740 1741 1742 1743 1744 1745
S: * SEARCH 1746 1747 1748 1749 1750 1751 1752 1753 1754 1755 1756 1757 1758 1759 1760 1761 1762 1763 1764 1765 1766 1767 1768 1769 1770 1771 1772 1773 1774 1775 1776 1777 1778 1779 1780 1781 1782 1783 1784
S: * SEARCH 1785 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 1796 1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809 1810 1811 1812 1813 1814 1815 1816 1817 1818 1819 1820 1821 1822 1823
S: * SEARCH 1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835 1836

Is this the intended behavior? Is the server not allowed to split response?