If you've noticed that emails sent through eBoss occasionally land in a recipient's spam folder, even when the same email sent from your own Outlook arrives fine, this article explains why and what can be done about it.
WHY OUTLOOK AND eBoss BEHAVE DIFFERENTLY
When you send an email directly from Outlook, it travels via Microsoft's own infrastructure. If your recipient also uses Microsoft 365 -- which most UK businesses do -- the email is effectively moving Microsoft-to-Microsoft on a trusted internal corridor. Spam filters like Mimecast and Microsoft Defender extend high baseline trust to this traffic by default.
When eBoss sends an email on your behalf, it goes through SendGrid, a specialist email delivery service used by virtually every recruitment platform on the market, including Bullhorn, Vincere, and JobAdder. This gives you:
Open and click tracking
Bounce and delivery reporting
Bulk candidate distribution without triggering Microsoft 365 outbound throttle limits
Separation of your personal mail reputation from recruitment activity
The trade-off is that all third-party sending services face higher default scrutiny from enterprise spam filters. This is by design: filters categorise email service providers as higher-risk until sufficient authentication signals are in place. It applies equally to every ATS vendor on the market.
This is not a fault on either side. It is how the email ecosystem is designed.
WHAT AFFECTS YOUR DELIVERABILITY THROUGH eBoss
Domain authentication (DKIM and SPF)
Verifies that eBoss is authorised to send email on behalf of your domain. When correctly configured, it removes the "via sendgrid.net" tag from your outbound emails and significantly improves trust scores. Contact support if you are unsure whether this is set up on your account.
Link branding
When eBoss tracks opens and clicks, it rewrites tracking links in your emails. If link branding is not configured, those links show as sendgrid.net URLs rather than your own domain. Spam filters treat this as a trust signal mismatch and score the message lower. Link branding requires two CNAME records added to your domain DNS -- contact your eBoss account manager for these.
DMARC policy
DMARC tells receiving mail servers what to do if an email fails authentication checks. A policy of p=none (monitoring only) is treated by strict filters as incomplete setup and can reduce trust scores. Tightening this progressively -- none, quarantine, then reject -- alongside a reporting address improves deliverability over time.
Manually blocked recipients
If a recipient has personally marked your firm as a blocked sender in their own email client, no sending platform can override that. Repeat attempts to a blocked address count against your sending reputation. eBoss automatically suppresses future sends to addresses that return a manual-block bounce.
Identical subject lines sent in bulk
Sending emails with identical subject lines to multiple recipients at different companies within a short window is a pattern that Mimecast and Microsoft Defender are tuned to detect. Introducing minor per-recipient variation in subject lines removes this signal.
WHAT YOU CAN DO
In order of impact:
Ensure domain authentication is configured and valid. Contact eBoss support if unsure.
Set up link branding. Ask your eBoss account manager for the two CNAME records needed.
Review your DMARC record. If set to p=none with no reporting address, ask your DNS provider to tighten it progressively.
Request whitelisting from key clients. Ask their IT team to add your domain to their Mimecast or Microsoft 365 permitted senders list. This overrides tenant-level filtering permanently.
Maintain list hygiene. Remove recipients who have previously bounced or blocked you from outbound campaigns.
STILL HAVING ISSUES?
Contact eBoss support with a SendGrid delivery report if you have one. We can run a full diagnostic on your subaccount and identify exactly what needs attention.