prod_settings_template: Document email mirror needs MX records.
prod_settings_template: Document email mirror needs MX records.

The docs are still pretty much written for expert sysadmins, but this
should help a lot in avoiding confusing about what step is missing.

punchagan/zulip,shubhamdhama/zulip,hackerkid/zulip,eeshangarg/zulip,showell/zulip,rishig/zulip,hackerkid/zulip,rishig/zulip,rishig/zulip,showell/zulip,dhcrzf/zulip,rht/zulip,dhcrzf/zulip,hackerkid/zulip,dhcrzf/zulip,eeshangarg/zulip,rht/zulip,rishig/zulip,dhcrzf/zulip,rht/zulip,timabbott/zulip,hackerkid/zulip,rishig/zulip,synicalsyntax/zulip,synicalsyntax/zulip,synicalsyntax/zulip,timabbott/zulip,zulip/zulip,kou/zulip,synicalsyntax/zulip,kou/zulip,timabbott/zulip,zulip/zulip,eeshangarg/zulip,jackrzhang/zulip,andersk/zulip,dhcrzf/zulip,timabbott/zulip,rishig/zulip,dhcrzf/zulip,zulip/zulip,andersk/zulip,hackerkid/zulip,punchagan/zulip,tommyip/zulip,zulip/zulip,punchagan/zulip,kou/zulip,eeshangarg/zulip,synicalsyntax/zulip,shubhamdhama/zulip,brainwane/zulip,rht/zulip,dhcrzf/zulip,punchagan/zulip,kou/zulip,brainwane/zulip,tommyip/zulip,synicalsyntax/zulip,shubhamdhama/zulip,showell/zulip,shubhamdhama/zulip,andersk/zulip,showell/zulip,rht/zulip,rht/zulip,jackrzhang/zulip,jackrzhang/zulip,eeshangarg/zulip,andersk/zulip,kou/zulip,zulip/zulip,hackerkid/zulip,timabbott/zulip,punchagan/zulip,andersk/zulip,jackrzhang/zulip,rht/zulip,shubhamdhama/zulip,andersk/zulip,punchagan/zulip,eeshangarg/zulip,timabbott/zulip,eeshangarg/zulip,tommyip/zulip,tommyip/zulip,tommyip/zulip,brainwane/zulip,tommyip/zulip,brainwane/zulip,brainwane/zulip,jackrzhang/zulip,hackerkid/zulip,andersk/zulip,jackrzhang/zulip,showell/zulip,synicalsyntax/zulip,tommyip/zulip,timabbott/zulip,brainwane/zulip,kou/zulip,rishig/zulip,jackrzhang/zulip,showell/zulip,shubhamdhama/zulip,zulip/zulip,zulip/zulip,showell/zulip,shubhamdhama/zulip,punchagan/zulip,brainwane/zulip,kou/zulip