Sending.ac
Alternative & Review

The company was founded in 2024 by Yannic Schwock, Felix Seidel, Dharmendra Soni, and Thierry Maftoum.

Sending.ac positions itself as a provider of Azure-based cold email infrastructure; the platform highlights automated DNS setup and a focus on keeping emails out of spam folders. They also emphasize 100% isolation with a dedicated Azure outbound tenant per domain and avoid shared IPs, with automatic replacement every 14 days.

The company has no reviews on G2 or Trustpilot.

• "A lot of these were burned last month, mass microsoft tenant shut downs. Since then, a little bit sketchy."
• "you're correct, most microsoft infra providers got burned a few weeks ago. I did some digging on that and found the CEO of sending.ac talking about that very shutdown."

sending.ac : r/coldemail

🟢 Dedicated Azure outbound tenants. Sending.ac offers 100% isolation with a dedicated Azure outbound tenant per domain, enhancing deliverability and security.
🟢 No shared IPs with automatic rotation. The service ensures no shared IPs, with automatic replacement every 14 days, which helps maintain sender reputation.
🟢 Automated and fast mailbox setup. Mailbox setup is fully automated and quick, taking approximately 34 seconds per mailbox.

🔴 High minimum order. A minimum order of 450 mailboxes might be restrictive for smaller users or those just starting.
🔴 API access not publicly found. Information regarding API access for programmatic control is not readily available on their public res.
🔴 Self-healing features not explicitly mentioned. Beyond general isolation claims, specific self-healing or recovery features are not explicitly detailed.

Maildoso isn’t a complex management suite or a sequence builder – we know that real outreach needs a rock-solid foundation. We understand how the inbox works way better than those "all-in-one" platforms. From our self-healing mailbox rotation to automated email deliverability infrastructure checks, we do all the technical "dirty work" for you, so you can stop worrying about the tech and get back to closing deals.

We provide high-authority mailboxes designed to stay healthy for months, not weeks, allowing your outreach team to focus on the 1% of deals that matter rather than the 99% of tech that usually breaks. It’s a specialized environment for agencies looking for a reliable SMTP mailbox for agencies that have graduated from generalist tools.

G2: 4.7/5 (181 reviews)

"For the price point it's been worth it for us. We're sending around 1,500-2,000 emails/day across those 100 mailboxes and reply rates have been decent (2.8-3.2% depending on the campaign, but that's more about copy and targeting obviously). The infrastructure has been stable enough that i'm not constantly putting out fires anymore which was the whole point." (My Maildoso review after testing 100 mailboxes over 3 months)

"Checking back in after another 14 days of volume. We’re officially at 500 mailboxes now and the infrastructure is holding up remarkably well. Only 14 boxes are currently in the "cooling off" period, which is less than 3% of the fleet (totally manageable). Reply rates are hovering at 2.3%, keeping our cost per reply at that $0.10 mark. Honestly, the biggest win so far isn't just the price, it’s the lack of "clustering" issues that usually plague us at this volume on GW. (The truth about SMTP in 2026: A very deep Maildoso review (300k emails sent))"

🟢 Dynamic IP Rotation: We don't just "aim" for the inbox – we engineer it. Our system automatically rotates your IP addresses in real-time. If an IP gets flagged or blacklisted, we instantly swap it for a clean one before your campaign takes a hit, ensuring your emails consistently land in the primary inbox rather than getting stuck in spam.
🟢 Self-Healing Rotation System: An automated resting period for mailboxes every two weeks that clears provider flags and recovers reputation on autopilot.
🟢 Hybrid Flexibility: The ability to seamlessly blend high-authority Google Workspace accounts with high-volume SMTP mailboxes.
🟢 Global Customer Domain Tracking: Proprietary technology that allows you to safely include links without compromising your sender reputation.
🟢 Automated Inbox Placement Tests: Free email deliverability infrastructure testing every three days for all mailboxes, giving you real-time visibility into your health.
🟢 Unlimited Technical Audits: Free live sessions with experts who resolve up to 80% of issues through deep server-level forensic audits.
🟢 Advanced Captcha Protection: Technical barriers that shield your outreach domains from being linked back to your primary corporate assets.

🔴 Conservative Limits: We suggest sticking to 15 emails a day per box to keep your domains healthy for the long run. You are free to send more if you choose, but be aware that aggressive "blasting" is a fast track to burning your reputation.
🔴 Google/SMTP Focus: We do not support native Microsoft 365/Outlook environments at this time.

We generally advise against using Sending.ac.

The issue isn’t necessarily with this specific product, but rather with Azure tenants as a whole. Despite their low cost, these accounts simply cannot send a sufficient volume of emails (only 2–4 per day). Furthermore, we frequently hear reports of Azure tenants being blacklisted by email service providers, often leading to a total infrastructure ban that forces the provider to shut down entirely.

If you don't currently have any mailboxes, it's better to start with more reliable providers like Maildoso, Zapmail, or Scaledmail. On the other hand, if you already have an established setup and are simply looking to experiment, there are other Azure tenant providers on the market offering much more flexible and affordable entry-level plans.