A tenant's administrator can turn legacy mail apps off for the organization

INBUXA's tenant switch (legacy-protocols LP-9 to LP-18) in the
administration. Each tenant's sheet gains "Legacy mail apps": whether IMAP,
POP3, ManageSieve and sending from mail apps are on or off on the tenant's
domains, and the switch.

Nobody turns it off by accident. "Turn off legacy protocols…" first shows
who would notice -- every account in the tenant that signed in with a
legacy mail app in the last 30 days, with the protocols and when (LP-15) --
and the statement of what it means, "for everyone in {tenant}" (LP-16),
then asks for the phrase "turn off legacy mail", matched exactly (LP-17).
Turning it back on is one click; the server refuses while it has legacy
protocols off for everyone, and its words are shown. A tenant's switch
closes no port, so the statement names none.

It needs the domain permissions the server checks for the switch; with
read-only access the state shows and the buttons don't. On a server that
isn't INBUXA, or is older, the section isn't there.

The dashboard says so while legacy mail is off for the signed-in
administrator's organization (LP-18), from the same session flag as
Settings › Security's line.

Every new string in all nine languages, the register each catalog uses, and
the count in each language's plural forms.

web/src/locales/zh-Hans.ts

@@ -1701,8 +1701,29 @@ export const catalog: Catalog = {
     "{app} will tell you if a later message from this address is signed by anybody else.": "如果此地址之后的邮件由他人签名，{app} 会提醒您。",
     "itself, or an issuer it does not name": "其自身，或一个未具名的颁发者",
     "no address": "无地址",
+    // ── Administration: legacy mail protocols (INBUXA) ──────────────
+    "Legacy mail apps": "使用传统协议的邮件应用",
+    "Off for {tenant}. Only {app} and JMAP apps can sign in to its domains.": "{tenant} 已关闭。只有 {app} 和 JMAP 应用可以登录其域名。",
+    "On for {tenant}. Mail apps can use IMAP, POP3 and ManageSieve on its domains.": "{tenant} 已开启。邮件应用可以在其域名上使用 IMAP、POP3 和 ManageSieve。",
+    "Turn legacy protocols back on": "重新开启传统邮件协议",
+    "Turn off legacy protocols…": "关闭传统邮件协议…",
+    "No account used a legacy mail app in the last 30 days.": "过去 30 天内没有账户使用过传统协议的邮件应用。",
+    "Their mail apps will stop working the moment you turn this on:": "您开启此项后，这些账户的邮件应用将立即停止工作：",
+    "Only {app} and JMAP apps will work.": "只有 {app} 和 JMAP 应用可以使用。",
+    "Legacy mail protocols (IMAP, POP3, ManageSieve and sending from mail apps) will be turned off for everyone in {tenant}.": "{tenant} 中所有人的传统邮件协议（IMAP、POP3、ManageSieve 以及从邮件应用发信）都将被关闭。",
+    "Phone and desktop mail apps will stop receiving and sending mail. That's iPhone and iPad Mail, the Gmail and Outlook apps, Outlook, Thunderbird and Apple Mail. People will see sign-in errors in them.": "手机和电脑上的邮件应用将无法收发邮件，包括 iPhone 和 iPad 上的邮件、Gmail 和 Outlook 应用、Outlook、Thunderbird 以及 Apple Mail。用户会在这些应用中看到登录错误。",
+    "Filters managed from a mail app (ManageSieve) will stop working. Filters set in {app} keep working.": "通过邮件应用管理的过滤器（ManageSieve）将停止工作。在 {app} 中设置的过滤器会继续工作。",
+    "Incoming mail is not affected. Calendars and contacts are not affected.": "收件不受影响。日历和联系人不受影响。",
+    "People keep full access through {app}, which can be installed as an app on phones and computers.": "所有人仍可通过 {app} 完整访问，{app} 可以作为应用安装在手机和电脑上。",
+    "Sending from mail apps (SMTP submission) will stop working, but its ports stay open: mail apps will be told they cannot sign in. Incoming mail (SMTP) and {app} (JMAP) are not affected and cannot be turned off here.": "从邮件应用发信（SMTP submission）将停止工作，但其端口保持开放：邮件应用会被告知无法登录。收件（SMTP）和 {app}（JMAP）不受影响，也无法在此关闭。",
+    "You can turn legacy protocols back on at any time.": "您可以随时重新开启传统邮件协议。",
+    "To confirm, type {phrase}": "请输入 {phrase} 以确认",
+    "Turn off legacy protocols": "关闭传统邮件协议",
+    "Legacy mail protocols are off for your organization. Only {app} and JMAP apps can sign in.": "您的组织已关闭传统邮件协议。只有 {app} 和 JMAP 应用可以登录。",
   },
   plurals: {
+    // ── Administration: legacy mail protocols (INBUXA) ──────────────
+    "{n} accounts used a legacy mail app in the last 30 days.": {other: "过去 30 天内有 {n} 个账户使用过传统协议的邮件应用。"},
     // ── Administration: domains ────────────────────────────────────
     "{n} accounts use this domain. Move or delete them first.": { other: "有 {n} 个账户正在使用此域名。请先移动或删除它们。" },
     "The server stops accepting mail for this domain, and its {n} DKIM keys are deleted. This can't be undone.": { other: "服务器将不再接收此域名的邮件，其 {n} 个 DKIM 密钥也会被删除。此操作无法撤销。" },