Best Email Continuity Services For Microsoft 365 In 2027

Last updated: November 14, 2026

The best email continuity services for Microsoft 365 in 2027 are Mimecast Mailbox Continuity, Proofpoint Essentials Emergency Inbox, Hornetsecurity Continuity Service, Barracuda Email Protection and Retarus Email Continuity. Mimecast is the most complete option for larger companies, Proofpoint Essentials is the easiest for small businesses because its emergency inbox switches on by itself, and Hornetsecurity offers the best bundle of continuity, security and backup in one plan.

On November 12, 2026, Exchange Online servers began failing health checks, and Outlook, Teams and Copilot were down or degraded for businesses around the world into November 14. Companies whose mail flowed through a continuity service kept sending and receiving from an emergency inbox. Mimecast, for example, told its customers to switch to its Personal Portal, mobile apps or Outlook plug-in while Microsoft worked the problem. Everyone else waited.

An email continuity service sits in front of Microsoft 365 as your mail gateway. It accepts and queues inbound mail all the time, and when Microsoft goes down it gives your users a separate inbox to read and reply from, then syncs everything back once Microsoft recovers. A backup (see our list of Microsoft 365 backup solutions) protects old data; continuity keeps the business talking.

Email Continuity Services At A Glance

Company	Headquarters	Founded	Best For	Pricing
Mimecast Mailbox Continuity	London, UK	2003	Mid-size and large companies	Quote-based, part of Mimecast suites
Proofpoint Essentials	Sunnyvale, CA	2002	Small businesses that want automatic failover	Quote-based, sold mainly through partners
Hornetsecurity Continuity Service	Hanover, Germany	2007	Continuity, security and backup in one plan	Bundled in 365 Total Protection plans
Barracuda Email Protection	Campbell, CA	2003	Existing Barracuda customers	Quote-based, bundled tiers
Retarus Email Continuity	Munich, Germany	1992	Enterprises that want a non-Microsoft fallback	Quote-based
Intermedia Email Continuity	Sunnyvale, CA	1995	Small and mid-size US businesses	Quote-based, often via partners
N-able Mail Assure	Burlington, MA	2000	MSPs managing many client tenants	Per-mailbox, MSP pricing
MailRoute	Los Angeles, CA	2003	Regulated SMBs and government contractors	Tiered plans; 30-day free trial
OpenText Core Email Continuity	Waterloo, Canada	1991	OpenText and Zix customers	Quote-based
Microsoft Exchange Online Protection queueing	Redmond, WA	1975	Baseline only; not a substitute	Included with Microsoft 365

Best Email Continuity Services For Microsoft 365 In 2027

1. Mimecast Mailbox Continuity — The Most Complete Continuity Layer For Microsoft 365

Mimecast has sold email continuity for Microsoft 365 longer than almost anyone, and it showed this week. Users can keep working in Outlook through the Mimecast plug-in, which can switch into continuity mode within about 15 minutes of an Exchange outage, or through the web portal and mobile apps. Mimecast supports continuity for up to seven days per event.

The catch is that Mimecast must be your mail gateway, so your MX records point to Mimecast all the time, and continuity comes as part of a wider security and archiving suite. Reported bundle pricing runs roughly $7 to $10 per user per month. For companies that want security, archiving and continuity from one vendor, that is the point.

2. Proofpoint Essentials — Emergency Inbox That Switches On By Itself

Proofpoint Essentials is Proofpoint’s small-business email security line, sold mainly through MSPs. Its Emergency Inbox activates automatically when it detects a Microsoft 365 email outage, with no administrator action needed, which is exactly what a small company with no IT staff on call needs at 11 p.m.

Continuity is an option on higher Essentials plans rather than built into every tier, so check that the plan you are quoted includes it. Pricing runs through partners.

3. Hornetsecurity Continuity Service — Continuity That Activates In Seconds, Bundled With Backup

Hornetsecurity, part of Proofpoint since 2025, includes its Continuity Service in the higher tiers of 365 Total Protection. When Microsoft 365 fails, continuity activates automatically within seconds and users reach mail through webmail, POP3 or an Outlook plug-in.

The same plan can include spam filtering, encryption, archiving and Microsoft 365 backup. For small and mid-size businesses, and especially European ones, that makes Hornetsecurity one of the simplest ways to cover both “my mail is down” and “my data is gone” with one vendor.

4. Barracuda Email Protection — Continuity Included In The Security Bundle

Barracuda bundles email continuity into its Email Protection plans alongside its gateway, anti-phishing and backup products. When Microsoft 365 is unavailable, Barracuda spools inbound mail and gives users an emergency mailbox, failing over automatically.

Know the limit: Barracuda’s continuity mode switches off after 96 hours. This week’s outage stretched past that for some tenants, so if long outages worry you, compare it against Mimecast’s seven days.

5. Retarus Email Continuity — Pre-Provisioned Inboxes Built Deliberately Outside Microsoft

Retarus is a privately owned German cloud provider that runs its own data centers, and its continuity service was intentionally not built on Microsoft technology. It keeps ready-to-use webmail inboxes provisioned for every user and synced with your directory in normal operation, so failover is a switch-over rather than a scramble.

Failover is triggered on request after a short process agreed in an onboarding workshop, which suits enterprises that prefer a controlled switch. Retarus generates a large share of its revenue in the US, so American support is not an afterthought.

6. Intermedia Email Continuity — Browser-Based Continuity Portal From A Hosted-Exchange Veteran

Intermedia made its name hosting Exchange for small businesses and now offers Email Continuity for Microsoft 365. During an outage, users send and receive through Intermedia’s browser-based continuity portal, and mail syncs back when Microsoft recovers.

It is a practical choice for US SMBs that already use Intermedia for phone systems or archiving, and it is widely available through IT resellers.

7. N-able Mail Assure — Multi-Tenant Continuity Built For MSPs

Mail Assure is N-able’s cloud email security and continuity service, designed for managed service providers who run dozens or hundreds of client domains from one console. It filters inbound mail, archives it and keeps a 24/7 emergency mailbox available when Microsoft 365 or Exchange is down.

If your IT is managed by an MSP on N-able tools, ask them to switch continuity on. It is often a small per-mailbox add-on rather than a new contract.

8. MailRoute — Always-On Continuity With A Rolling 30-Day Mail Store

MailRoute is a founder-led, self-funded email security company whose founding team previously built the filtering technology that Microsoft acquired in 2005. Its continuity is built into the MX layer and keeps a rolling 30-day store of clean mail at all times, so users are not waiting for a spool to start after the outage begins.

Continuity is included in its Enterprise tier, and there is a 30-day free trial with no credit card. It is a strong fit for regulated small businesses, MSPs and government contractors that want an independent vendor.

9. OpenText Core Email Continuity — Enterprise Continuity From The Zix Lineage

OpenText inherited a continuity product through its acquisitions in the email security space, and it now sells it as Core Email Continuity alongside its encryption and archiving tools. During an outage users reach mail through a web portal and the service stores mail for a set number of days.

It is most relevant if you already use OpenText or Zix for encryption or archiving. Buyers starting fresh will usually find Mimecast or Hornetsecurity easier to evaluate.

10. Microsoft Exchange Online Protection queueing — What You Get Without A Continuity Service

We include Microsoft’s built-in behavior so you can see the baseline. Exchange Online Protection queues and retries inbound mail during some failures, so messages may not be lost, but your users have no inbox to work from while Microsoft is down and no way to send.

That is fine if your business can stop emailing for a day. Most sales, support and legal teams cannot, which is why every other entry on this list exists.

How We Evaluated

We looked at how each service detects an outage and fails over (automatic or admin-triggered), how users reach mail during the outage (Outlook plug-in, web portal, mobile app), how long continuity mode can run, how much pre-outage mail history is available, whether the product requires rerouting your MX records, and what else is bundled. We used vendor documentation and status pages from the November 2026 outage. Rankings are editorial. See our research and ranking method.

How To Choose An Email Continuity Service

Do you want automatic or manual failover?

Automatic failover (Proofpoint Essentials, Hornetsecurity, Barracuda) is better for small teams with no one on call. Admin-triggered failover (Mimecast, Retarus) gives larger IT teams control and avoids flipping users into continuity mode during a short blip.

How long can continuity run?

This week’s outage ran for more than a day for many tenants. Check the maximum continuity period: Barracuda stops at 96 hours, Mimecast supports up to seven days per event.

Will users see their recent email history?

Some services only show mail received after the outage starts. Others keep a rolling store, such as MailRoute’s 30 days, so users can still find the thread they were working on.

Are you willing to change your MX records?

Most continuity services work as your mail gateway, which means your MX records point to them full time. That also gives you their spam and phishing filtering, but it is a real architecture change, so plan the cutover.

Can you get it from your existing vendor?

If you already use Mimecast, Proofpoint, Barracuda or an MSP on N-able, continuity may be a checkbox away. Ask before you buy a new product.

Frequently Asked Questions

What is email continuity?

Email continuity is a service that keeps your company able to send and receive email when your main email platform, such as Microsoft 365, is down. It queues inbound mail and gives users a temporary inbox, then syncs everything back once service returns.

Is email continuity the same as backup?

No. A backup protects existing data so you can restore it after deletion or ransomware. Continuity keeps new mail flowing during an outage. Most businesses that depend on email need both.

Did email continuity work during the November 2026 Microsoft 365 outage?

Yes. Customers with continuity services such as Mimecast were directed to emergency access through portals, apps and Outlook plug-ins while Exchange Online was degraded.

What is the best email continuity service for a small business?

Proofpoint Essentials and Hornetsecurity are the easiest for small businesses because failover is automatic and continuity can be bundled with security and backup.

Conclusion

Mimecast is the most complete continuity layer for mid-size and larger companies, Proofpoint Essentials is the easiest for small businesses, and Hornetsecurity is the best value if you want continuity, security and backup in one plan. If your business could not afford to go dark for a day this week, put one of these in front of Microsoft 365 now.

Continuity is one piece of the plan. See our guide on what to do when Microsoft 365 is down, our list of Microsoft 365 backup solutions, and the Cybersecurity And IT Services hub.