--- title: "Bounces when sending to certain recipients" description: "Why cold emails bounce or never arrive when the recipient's company uses a Secure Email Gateway (SEG) such as Proofpoint, Mimecast, Barracuda or Cisco, and why we recommend leaving those contacts out." url: https://help.salesforge.ai/en/articles/10175550-bounces-when-sending-to-certain-recipients collection: "Deliverability & Compliance" updated: 2026-10-26 language: en --- # Bounces when sending to certain recipients Why cold emails bounce or never arrive when the recipient's company uses a Secure Email Gateway (SEG) such as Proofpoint, Mimecast, Barracuda or Cisco, and why we recommend leaving those contacts out. Some recipients never receive your cold emails, or the emails bounce straight away, even though your domain, mailboxes and DNS are set up correctly. In most of these cases the recipient's company uses a **Secure Email Gateway (SEG)**, a security product such as Proofpoint or Mimecast that checks every incoming email before it reaches the inbox. This article explains what a SEG is, why cold emails struggle against one, and why we recommend not sending cold emails to these contacts. ## The short answer - Contacts behind a SEG are very hard to reach with cold email. The gateway is built to stop unsolicited outreach, and the recipient's company decides how strict it is. - Sending to them usually means bounces, quarantined emails and no replies, and the bounces can hurt your domain's reputation. - Salesforge shows you which contacts are behind a SEG when you validate them, so you can leave them out of your email sequences before you send. ## What is a Secure Email Gateway (SEG)? A Secure Email Gateway is an email security layer that a company puts in front of its normal email provider, such as Google Workspace or Microsoft 365. It is usually set up by changing the company's MX records, so every incoming email passes through the gateway first. The gateway scans the email and decides whether to deliver it, send it to junk, hold it in quarantine or reject it. Only then does it reach the employee's inbox. SEGs are designed to protect employees from phishing, malware and spam. Because they can't tell the difference between a legitimate cold email and unsolicited bulk email, cold outreach is treated with suspicion by default. The company's IT team configures the rules, so the same email can be delivered to one company and blocked by another. ### Which email security services are SEGs? The most common ones are:

Gateway	Also known as	Usually visible in the recipient's MX records as
Proofpoint	Proofpoint Email Protection, Proofpoint Essentials	pphosted.com
Mimecast	Mimecast Email Security	mimecast.com
Barracuda	Barracuda Email Security Gateway	barracudanetworks.com
Cisco	Cisco Secure Email (formerly IronPort)	iphmx.com

Others include Trend Micro, Sophos, Forcepoint and Symantec email security. Large companies, government bodies and organizations in regulated industries such as finance, healthcare and education are the most likely to use one, although smaller companies can too. Most small and mid-size B2B companies host their email on Google Workspace or Microsoft 365 without an extra gateway. ## Why cold emails bounce or disappear behind a SEG SEGs look at many signals at once. No single fix gets around all of them, and the exact rules are set by each recipient's company. - **Sender reputation.** The gateway checks the reputation of your domain and sending IP. A new domain, missing SPF, DKIM or DMARC, or a history of spam complaints makes blocking more likely. - **Content and links.** Salesy wording, many links, tracking links, link shorteners and attachments draw extra scrutiny. Many gateways rewrite links and scan them again when the recipient clicks. - **Sending patterns.** Sudden jumps in volume, many emails to one company in a short time, and the typical patterns of cold email tools can trigger rate limits or blocks. - **Known cold email infrastructure.** Gateways learn to recognize mail that comes from outreach tools and custom SMTP servers, and they are often stricter with it. - **Blocklists.** Some gateways check domain and IP blocklists, so a listing can cause a bounce at those companies only. See [our SURBL article](https://help.salesforge.ai/en/articles/10333633-my-domain-is-on-the-surbl-blacklist-is-that-a-problem.md) for an example. - **Greylisting.** Some gateways, such as Mimecast, temporarily defer mail from unknown senders and expect a retry. This delays or drops emails that don't retry properly. - **Company-specific rules.** IT teams can block mail from unknown or unapproved senders outright, or set very aggressive filters. Even a well-written, well-targeted cold email can get caught. - **Unverified lists.** Invalid addresses and spam traps in your list are penalized more heavily than elsewhere. ### What it looks like when a SEG blocks you - **A bounce.** The email is rejected right away and you get a bounce. The message often names the security service or a blocklist. - **A temporary deferral.** The gateway asks your server to try again later. Your emails are delayed, and some are never delivered. - **Quarantine or junk.** The email is accepted, so you see no bounce, but it is held for the IT team or hidden in junk. The recipient never sees it, and you just see no replies. This is a deliberate security decision by the recipient's company, so warm-up, a cleaner domain or different wording can't reliably get around it. ## Why you should avoid sending cold emails to these contacts 1. **Risk of domain reputation damage.** Repeated bounces and blocks from SEGs count against your sending domain, which makes your emails less likely to reach other recipients too, including people who use Google or Microsoft 365. 2. **High likelihood of non-engagement.** Protected companies are usually larger and stricter. Even when an email is delivered, it often lands in quarantine or junk, so replies are rare. 3. **Effort versus reward.** Trying to work around a gateway by changing content or sender details takes a lot of effort and rarely works. Your time is better spent on contacts you can actually reach. 4. **Compliance and legal risks.** Repeatedly emailing recipients whose company has chosen to block outreach can be seen as spam under rules such as GDPR and CAN-SPAM, especially without consent. ## How Salesforge helps you avoid them When you validate contacts in Salesforge, the validation screen shows which email provider or security service each contact uses. This is the **ESP** information. It is separate from the validation status: a contact can be **Safe**, meaning the address is valid and can receive email, and still sit behind a gateway that blocks cold emails. ESP data is only available after a contact has been validated. - **ESP column.** Every contact has an icon for its provider, for example Microsoft 365 or Google. - **ESPs filter.** The left panel lists each provider with the number of contacts, so you can include or exclude whole groups. On the Safe tab these are providers such as Microsoft 365 and Google (professional), Outlook, Gmail, iCloud, Mail.com, Yandex, Yahoo and Other. - **Proofpoint and Anti Spam Software.** On the Unsafe tab, contacts behind **Proofpoint** are listed under their own name. Contacts behind other security gateways are grouped as **Anti Spam Software**. ![Salesforge validation screen, Unsafe tab, with the ESP column and the Proofpoint and Anti Spam Software filters](https://staticfiles.gleap.io/p677a7ec3b682e732d0e54ed0/othfJPghgpBSsd3zSa0rlAIYe9GxpXaDQaZJvl5440aSJhP6IVbtKnqTfXBtDBNaCqA0cYf89GD.png) ![Salesforge validation screen, Safe tab, with the Statuses and ESPs filters](https://staticfiles.gleap.io/p677a7ec3b682e732d0e54ed0/ojqrPucrC9TqCgnZ0j7iwL9DmTbjDxLILcrgw5VUxicaEdqXcLtryq9sr1BN7YCyyqOMdNeyxTu.png) ## What to do 1. **Validate your contacts before you add them to a sequence.** Validation is what detects the provider each contact uses. 2. **Leave out Proofpoint and Anti Spam Software contacts** in your email sequences. Use the ESPs filter to exclude them before you add the contacts. 3. **Reach them another way.** For important accounts behind a gateway, a channel such as LinkedIn, a phone call or a referral works better than cold email. 4. **If you still want to email them, keep it light.** Send from a separate domain so your main domains stay clean, use plain text, keep links to a minimum, avoid attachments and tracking, and send low volumes. Expect lower results. 5. **Watch your bounces.** If a few bounces name a security service or blocklist, they come from these recipients. Remove those contacts from your sequences and carry on as normal with the rest. ## How to check if a company uses a SEG yourself Look up the recipient domain's MX records with a free tool such as MXToolbox. If the records point to a hostname containing pphosted.com, mimecast.com, barracudanetworks.com or iphmx.com, the company uses Proofpoint, Mimecast, Barracuda or Cisco. If they point to Google or Microsoft, the mail is hosted there directly. Some security tools connect directly to Google or Microsoft without changing the MX records, so MX records alone don't always show them. Salesforge's validation is the easier way to find these contacts. ## FAQ **Is the bounce caused by a problem with my domain or mailboxes?** Usually not. If your emails reach Google and Microsoft 365 recipients normally, the problem is the recipient's gateway, not your setup. **Can the recipient's company allow my emails through?** Their IT team can add your domain to an allow list, but that is a decision for each company and isn't something you can rely on for cold outreach. **Will warming up my mailboxes fix it?** Warm-up protects your reputation with Google and Microsoft 365, but it doesn't override a company's own security rules. **What does "Safe" mean if the contact is behind Proofpoint?** Safe means the address is valid and can receive email. The ESP tells you where it is hosted and whether a gateway protects it. **A bounce mentions SURBL. Is that a gateway too?** Yes. A few gateways and spam filters check SURBL, which is why only some recipients bounce. See our SURBL article for details and what to do.