According to Live Direct Marketing's daily Tranco top-1M scan (July 13, 2026), rexx systems is the SaaS sender for 221 domains — 0.04% of 617,702 SPF-publishing domains. Detection method: include: mechanisms in the SPF record.
Rexx Systems is an email transmission service that provides outbound mail delivery for organisations. Operating as a cloud-based SMTP relay, Rexx Systems allows customers to route transactional and application-generated messages through its infrastructure, with its authorised IP addresses typically referenced in customer domain SPF records.
The service is positioned in the long tail of smaller and mid-sized organisations rather than among global enterprises, with notable concentration in German-speaking markets (.de domain space). Its frequent appearance alongside Microsoft 365 in SPF configurations reflects a common hybrid architecture in which organisations use Microsoft platforms for employee email and collaboration whilst delegating transactional mail to specialist vendors. For email practitioners, this footprint pattern indicates Rexx Systems is an established service provider serving legitimate business use cases within the SME segment.
| Tranco rank band | Domains | Share of its base |
|---|---|---|
| Top 1,000 | 0 | 0.0% |
| Top 10,000 | 1 | 0.5% |
| Top 100,000 | 34 | 15.4% |
| Top 1,000,000 | 180 | 81.4% |
| Unranked | 6 | 2.7% |
| TLD | Domains | Share | |
|---|---|---|---|
| .de | 128 | 57.9% | |
| .com | 62 | 28.1% | |
| .at | 8 | 3.6% | |
| .ch | 8 | 3.6% | |
| .org | 4 | 1.8% | |
| .eu | 2 | 0.9% | |
| .biz | 2 | 0.9% | |
| .net | 1 | 0.5% | |
| .tv | 1 | 0.5% | |
| .sh | 1 | 0.5% |
Cross-tabulated from the same daily snapshot — the other email services seen on the same 221 domains.
| Type | Service | Domains | Share of rexx systems users |
|---|---|---|---|
| Mailbox | Microsoft 365 | 80 | 36.2% |
| Mailbox | Self-Hosted | 42 | 19.0% |
| Mailbox | Unknown / Other | 35 | 15.8% |
| Mailbox | Hornetsecurity | 13 | 5.9% |
| Mailbox | Generic / unmatched (mx*.*) | 12 | 5.4% |
| Mailbox | Proofpoint | 10 | 4.5% |
Rexx Systems is regularly observed in SPF records together with Microsoft 365, particularly in organisations based in German-speaking regions. This pattern reflects a deliberate architectural split in which Microsoft 365 manages employee communications and general corporate messaging, whilst Rexx Systems handles application-triggered transactional mail such as notifications, password resets, and automated reports. Recognising this coexistence helps email receivers understand legitimate multi-vendor mail flows and supports senders in designing compliant authentication strategies across their messaging infrastructure.
See the full rexx systems data page (KPI cards, trend, sample domains) →
Rexx Systems is an email transmission service that relays outbound mail on behalf of customer organisations; domains include Rexx Systems in their SPF records to authorise its IP addresses to send email. Its presence is especially common among smaller organisations in German-speaking markets, often configured alongside Microsoft 365 for hybrid mail delivery.
221 domains in the Tranco top-1M use rexx systems as their SaaS sender as of July 13, 2026 (0.04% of SPF-publishing domains), according to Live Direct Marketing's daily DNS scan.
rexx systems accounts for 0.04% of SPF-publishing domains in the top 1M. Whether you should seed a test mailbox there depends on how much of your audience it represents — the co-usage table above shows the services it appears alongside most.
rexx systems's largest TLD is .de (57.9% of its domains); it appears across 14 TLDs in total.