Email Deliverability

Email Deliverability: Whitelisting Crewmojo's Sending IPs

Article for: IT Administrators / Platform Administrators Applies to: All Crewmojo plans

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Overview

Crewmojo sends transactional emails - such as workflow notifications, check-in reminders, feedback requests, and account alerts - through Postmark, a dedicated transactional email service built for reliability and deliverability.

In most cases, these emails arrive in your inbox without any configuration on your end. However, organisations with strict email security policies, corporate firewalls, or aggressive spam filtering may find that Crewmojo emails are blocked or routed to junk folders before your employees ever see them.

Whitelisting Postmark's sending IP addresses is the most reliable way to resolve this.

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Why emails might be blocked

Enterprise email environments often apply inbound filtering rules at the gateway level - before a message even reaches a user's mailbox. Tools like Microsoft Defender for Office 365, Mimecast, Proofpoint, Barracuda, and similar platforms can silently quarantine or reject mail based on sender IP reputation, even when the sending domain is legitimate.

Because Crewmojo emails originate from Postmark's infrastructure (not directly from crewmojo.com mail servers), your mail gateway may not recognise the sending IPs as trusted, particularly if your policy defaults to blocking unknown sources.

Postmark recommends that recipients' IT or mail administration teams whitelist either your sending domain or Postmark's sending IP addresses in their spam filter settings Postmark to resolve these kinds of blocks.

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What to whitelist

Postmark publishes a dedicated support article listing all IP addresses used for sending, SMTP, inbound processing, and webhooks:

👉 Postmark IPs for Firewalls — postmarkapp.com/support/article/800-ips-for-firewalls

For Crewmojo emails specifically, you need the Outgoing Transactional sending IPs listed on that page. Postmark publishes CIDR ranges for transactional message sending, SMTP outbound endpoints, inbound MX records, and webhook source IPs. Postmark

Note: Postmark separates transactional and broadcast traffic onto different IP ranges. Crewmojo uses the Transactional stream only, so you can scope your whitelist rules accordingly.

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Steps for your IT team

1. Visit the Postmark IPs for Firewalls page to retrieve the current list of transactional sending IP ranges.

2. Add these CIDR ranges to your email gateway's inbound allowlist (sometimes called a "safe sender IP list" or "connection filter" depending on your platform).

3. Optionally, also whitelist the sending domain crewmojo.com and the bounce/return-path domain pm-bounces.crewmojo.com for belt-and-braces coverage.

4. Ask an affected user to send a test email notification from within Crewmojo (e.g. trigger a goal reminder) and confirm delivery.

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Keeping your whitelist up to date

Postmark publishes any changes to their IP ranges on their API and infrastructure updates page. If you send email using SMTP and explicitly whitelist Postmark's SMTP endpoint IPs, any newly added IPs will need to be added to your allowlist when Postmark announces them. Postmark

We recommend subscribing to Postmark's updates or periodically reviewing the IPs for Firewalls page to ensure your rules stay current.

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Still having issues?

If you've whitelisted the IPs and emails are still not arriving, it may point to a domain-level block or DMARC policy conflict. Contact Crewmojo Support at [email protected] and include:

• The email address(es) affected

• Your organisation's email domain (e.g. yourcompany.com)

• Any bounce or rejection messages your mail gateway is generating

We can work with your IT team to identify the root cause.