Cisco Secure Email Gateway End of Life (EOL) Dates & Support Timeline
Complete end-of-life dates, support windows, and security status for all Cisco Secure Email Gateway versions. Data sourced from endoflife.date and official vendor documentation. Updated at every deploy.
Cisco Secure Email Gateway 16.5 is supported until August 30, 2029, its end-of-support date. Active support for Cisco Secure Email Gateway 16.5 ends on August 30, 2027; security fixes continue until that end-of-life date. The next Cisco Secure Email Gateway version to reach end of life is 15.5 (FIPS compliant), on April 30, 2027. The full Cisco Secure Email Gateway lifecycle, with every version's release and end-of-support date, is in the table below.
Running an EOL version? Get matched with support options — free ↓| Version | Latest Release | Release Date | EOL Date | Days | Status |
|---|---|---|---|---|---|
| 15.0 (FIPS compliant) | 15.0 | Aug 10, 2023 | Apr 30, 2027 | 227 days remaining | Active |
| 15.5 (FIPS compliant) | 15.5.5-014 | Apr 30, 2024 | Apr 30, 2027 | 227 days remaining | Active |
| 16.0 | 16.0.4-302 | Oct 3, 2024 | Oct 30, 2027 | 410 days remaining | Active |
| 16.5 | 16.5.0-780 | Aug 10, 2026 | Aug 30, 2029 | 1080 days remaining | Active |
Live EOL badge for your README — updates automatically at every build.
[](https://endoflife.ai/cisco-secure-email-gateway)
Cisco Secure Email Gateway lifecycle status — the real story
Cisco Secure Email Gateway (formerly Email Security Appliance, ESA) AsyncOS software trains, from Cisco Secure Email Gateway Software Lifecycle Support Statement (PDF, published 2026-08-10, read 2026-09-14). Cisco publishes the table from AsyncOS 15.0 onward only; older trains (14.x, 13.x) have no support dates in the statement and are not served. Milestone mapping follows our Cisco ASA, FTD and FMC convention: releaseDate = Release Date (General Deployment), support = End of Software Maintenance Release (EoSMR), eol = End of Vulnerability and Security Support (EoVSS), extendedSupport = Last Date of Support. The statement defines EoSMR as 12 months after General Deployment (18 for FIPS/CC certified releases) and EoVSS and Last Date of Support as 36 months after General Deployment; the printed table is what is served where it departs from that rule (15.0 and 15.5 share an EoVSS of 2027-04-30).
Latest builds are the first fixed releases in Cisco advisory cisco-sa-esa-inj-2bLVGmhX (2026-09-14): 15.5.5-014, 16.0.4-302 and 16.5.0-780; 15.0 carries no fixed build in that advisory (its row is folded into 15.5 and earlier -> 15.5.5-014), so its latest is left at the train.
KEV context (CISA catalog 2026.09.14): CVE-2026-76461 under Cisco / Secure Email Gateway, added 2026-09-14, due 2026-09-17, forensic triage required; matched by the display name.
Cisco Secure Email Gateway release and support pattern
Across the 4 release lines with a published release date, Cisco Secure Email Gateway has shipped a new line roughly every 9 months (median interval). A line typically stays in standard support for about 3.1 years from its release to its standard-support end date.
Of the 4 release lines tracked, 0 are past end of life and 4 are still within support. The newest line, 16.5, was released August 10, 2026. The next scheduled end of life is 15.5 on April 30, 2027 — 227 days from this build. The longest-supported line currently published is 16.5, to August 30, 2029. Upstream also publishes an extended-support phase for 4 lines, shown in the table above.
Computed from the tracked release data at every build — the figures above are the dates in the table, restated, not an editorial estimate.
Cisco Secure Email Gateway security intelligence
CISA KEV history: Cisco Secure Email Gateway is named in CISA's Known Exploited Vulnerabilities catalog 1 time, most recently on 2026-09-14. Derived from CISA's live catalog at every build.
What does Cisco Secure Email Gateway end of life mean for your organization?
When a version of Cisco Secure Email Gateway reaches end of life, the maintainers stop issuing security patches. Vulnerabilities discovered after this date are publicly disclosed on the National Vulnerability Database, exploit code appears on GitHub, and your systems remain permanently exposed.
The CVE blind spot: Most vulnerability scanners check for known CVEs but do not flag the accumulation of unpatched vulnerabilities in EOL software. With a zero-day, nobody knows about the vulnerability. With EOL software, the vulnerability is public — listed, rated, and often weaponized — but no patch will ever exist. This is the most dangerous gap in enterprise security posture.
Organizations running EOL Cisco Secure Email Gateway should treat it as a vulnerability class in their risk register, apply compensating controls (network segmentation, enhanced monitoring, access restriction), and prioritize migration to a supported version.
Your options when Cisco Secure Email Gateway reaches end of life
There are four realistic paths. Which one is right depends far more on how long the system needs to keep running than on the version you are on today.
| Option | Best when | Watch out for |
|---|---|---|
| Move to a supported version | The system will outlive the current version's support window and you can schedule the work | Budget for compatibility testing, not just the upgrade itself — that is where the real cost sits |
| Replace the component | The project is unmaintained, or a better-supported alternative exists | The replacement has its own lifecycle and its own end-of-life date — you are changing vendors, not escaping the problem |
| Buy extended support | Migration is genuinely underway but cannot finish before the deadline, or the workload is frozen by certification or a third-party application | A bridge, not a destination — every year purchased is a year the migration still has to happen |
| Document accepted risk | The system is isolated, short-lived, or scheduled for retirement | Only defensible with real compensating controls and a written decision — auditors treat undocumented end-of-life software as a finding |
How to choose, in one question: how many more years does this system need to run? Under a year, extended support (where it exists) is usually cheaper than an emergency migration. One to three years, migrate — support purchased repeatedly costs more than doing the project once, and the project only gets harder as the version ages. Indefinitely, migrate now and plan the next migration before it surprises you.
Worth saying plainly, because vendors selling extended support rarely will: extended support is often the more expensive choice over a multi-year horizon. It is the right answer when a deadline is genuinely unreachable, not as a default. Compare the annual fee against the one-time cost of migrating before committing to either.
Formalizing decisions like this across your estate? Our free EOL policy template is a ready-to-adopt policy with risk tiers, remediation SLAs, and audit mapping — no signup, free to use and share.
Extended Support Options
If you cannot migrate immediately, extended support vendors provide continued security patches for EOL Cisco Secure Email Gateway versions. This is a bridge, not a permanent solution — plan your migration in parallel.
When Cisco Secure Email Gateway versions reach end of life, security patches stop — the CVEs keep coming. Extended support past the official date exists for many products in this position — whether it exists for Cisco Secure Email Gateway is exactly what we check. Tell us where to reach you and we'll reply with matched options and pricing guidance — or an honest "no vendor covers this."