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Why are my emails sent from Gmail SMTP ending up in spam folders in Outlook, Hotmail and Live?

Summary

Emails sent from Gmail's SMTP servers frequently encounter deliverability challenges, especially when targeting Microsoft-hosted inboxes like Outlook, Hotmail, and Live. While proper authentication (SPF, DKIM, and DMARC) is a crucial foundation, it's often not enough to guarantee inbox placement, particularly for transactional or bulk emails. This is because email providers like Microsoft employ sophisticated spam filtering algorithms that consider a multitude of factors beyond basic authentication, including sender reputation, content, and recipient engagement.

What email marketers say

Email marketers frequently express frustration with inconsistent deliverability, especially when sending through common platforms like Gmail's SMTP to services like Outlook or Hotmail. They often report that despite having proper technical setups (SPF, DKIM, DMARC), their emails still land in spam. This issue is particularly prevalent with transactional or cold outreach emails, even when recipients have technically opted in or have a relationship with the sender.

Marketer view

Email marketer from Email Geeks explains that even with small, opt-in audiences for PR and HR communications, reaching the inbox remains a significant challenge. This suggests that the issue extends beyond just sending unsolicited mail and points to deeper filtering mechanisms at play, particularly with Microsoft email services.

10 Mar 2020 - Email Geeks

Marketer view

A community member from Spiceworks Community observes that the problem often lies specifically with Microsoft's spam-filtering system. They note that Microsoft is the only provider consistently placing their emails directly into the spam box, indicating a unique challenge with Microsoft's filters compared to others.

20 May 2019 - Spiceworks Community

What the experts say

Deliverability experts consistently highlight that the core issue with emails from Gmail SMTP landing in spam for Outlook, Hotmail, and Live users often boils down to the nature of the mail being sent (even if solicited) and the reputation of shared IPs. They emphasize that recipient feedback, coupled with the high volume of unsolicited mail often associated with generic SMTP servers like Gmail's, can heavily influence filtering decisions, overriding even perfect authentication.

Expert view

Deliverability expert from Email Geeks suggests that if recipients are signaling to filters that mail is unwanted, the filter operators will invariably respect that feedback. This underscores the paramount importance of user engagement and consent over technical configuration alone, as spam complaints directly influence sender reputation.

10 Mar 2020 - Email Geeks

Expert view

A deliverability expert from Word to the Wise explains that mailbox providers (MBPs) often assign reputation scores to sending IPs based on the aggregated behavior of all senders using them. If a shared IP is used by many senders, and some are abusive, it can drag down the reputation for legitimate senders, leading to emails being filtered as spam.

14 Nov 2023 - Word to the Wise

What the documentation says

Official documentation from major mailbox providers like Microsoft and Google outlines specific requirements and best practices for senders to ensure high deliverability, particularly for bulk or commercial email. These guidelines go beyond basic authentication, emphasizing sender reputation, low complaint rates, clear unsubscribe options, and adherence to content policies. Failure to meet these broader criteria, even with proper technical setup, often results in emails being filtered to spam folders.

Technical article

Official Microsoft documentation states that IP reputation is paramount for deliverability to Outlook.com, Hotmail, and Live Mail users. They advise new IP addresses to warm up gradually to build a positive sending history and avoid being flagged as suspicious. This underscores the challenge with shared IPs that might have varied sending histories.

15 Feb 2024 - EmailLabs

Technical article

Microsoft's bulk email restrictions, as highlighted by MarTech, apply specifically to senders sending 5,000 or more emails to Outlook.com, Hotmail.com, and Live.com domains. This means that a sender's volume directly impacts the level of scrutiny their emails receive, requiring adherence to stricter guidelines even if using Gmail's SMTP.

18 Oct 2023 - MarTech

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