POP3/IMAP is not working outside domain for non admin users (Domain Admin Users)

Hi,
I Can not set <g class="gr_ gr_12 gr-alert gr_gramm gr_inline_cards gr_run_anim Grammar only-ins replaceWithoutSep" data-gr-id="12" id="12">outlook</g> for <g class="gr_ gr_13 gr-alert gr_spell gr_inline_cards gr_run_anim ContextualSpelling multiReplace" data-gr-id="13" id="13"><g class="gr_ gr_11 gr-alert gr_spell gr_inline_cards gr_disable_anim_appear ContextualSpelling" data-gr-id="11" id="11">non</g> admin</g> users outside the company with Pop3/IMAP
but the domain admins can easily connect to server using Pop3/IMAP