Why is there a sudden increase in Gmail spam filtering?

Email marketer from Neil Patel's Blog shares that sudden increases in spam filtering can be due to changes in Gmail's algorithm, triggered by a high volume of user-reported spam or phishing attempts. He suggests checking your sender reputation and ensuring proper email authentication (SPF, DKIM, DMARC).

Email marketer from Sender explains that temporary issues with Gmail's infrastructure could lead to incorrect filtering of emails. While rare, these glitches can cause a temporary spike in spam filtering.

Email marketer from StackExchange shares that poor list hygiene (sending to old or unengaged email addresses) can lead to higher spam complaints, triggering stricter filtering. They recommend regularly cleaning your email list to remove inactive subscribers.

Email marketer from Litmus shares insight that aggressive filtering can come about when Gmail rolls out new features which results in low inbox placement rates.

Email marketer from an Email Marketing Forum warns against using purchased email lists. They explain that these lists often contain invalid or spam trap addresses, leading to high bounce rates and spam complaints, which negatively impact sender reputation.

Email marketer from Reddit suggests that changes in email content can trigger spam filters. They advise reviewing recent email campaigns for potentially problematic keywords or phrases that might be associated with spam.

Marketer from Email Geeks reports seeing similar spikes with some of the users he interfaces with. He advises noting any actual deliverability impact, bounces, or changes in domain/IP reputation to gauge whether or not further investigation is needed.

Marketer from Email Geeks shares that they once had a 38% spike for a domain they don’t use in forms.

Email marketer from EmailToolTester explains that if your are on a shared IP address then you are vulnerable to the sending practises of other email marketers using that same IP. If one of those IP's is spamming, then your emails will also be marked as spam.

Email marketer from Mailjet explains that a sudden increase in spam filtering could be triggered by a sudden spike in email volume. They recommend gradually increasing email volume to build sender reputation and avoid being flagged as a spammer.

Email marketer from GlockApps shares that reduced email reputation leads to higher spam filtering. This can come about from reduced engagement metrics such as opens and clicks.

Expert from Word to the Wise, Laura Atkins, responds that Gmail can move previously inboxed emails to spam folders if there is an increase in complaints, or if the user no longer engages with the emails. They suggest focusing on list hygiene, and relevant content.

Expert from SpamResource explains that sudden shifts in Gmail spam filtering often correlate with algorithm updates designed to better identify and filter evolving spam tactics. These updates may impact senders who were previously compliant but now trigger new filters.

Documentation from Google Support explains that Gmail's spam filters are constantly updated to adapt to new spamming techniques. This can lead to fluctuations in the number of emails filtered as spam. They also mention user reporting of spam helps refine the filters.

Documentation from DKIM explains that not setting up DKIM correctly will make your emails vulnerable to spoofing. This will result in a higher likelihood of spam filtering.

Documentation from RFC explains the importance of SPF, DKIM and DMARC and how these are updated. DMARC policies in particular are changed frequently which causes emails which were previously delivered to now be filtered.

Documentation from Spamhaus explains the importance of IP and Domain reputation, and how these are used to determine spam filtering levels. If a domain/IP has been added to a blocklist recently this will suddenly cause higher spam filtering