What could cause a sudden spike in spam rate reported in Google Postmaster Tools?

Email marketer from ActiveCampaign suggests checking email authentication (SPF, DKIM, DMARC) to ensure emails aren't flagged as spoofed, and to review content for spam triggers. Using double opt-in is also helpful

Marketer from Email Geeks explains that it was a combination of two things, that the client was likely borderline and they accidentally remailed resulting in double sending just before the spike.

Email marketer from MarketingForum.com says to check for a sudden change in email content (using spam trigger words), a compromised account sending unauthorized emails, or a recent change in email infrastructure.

Email marketer from Reddit shares that they have seen spam spikes after a poorly executed email list cleaning or accidentally including a purchased list segment in a send.

Email marketer from Gmass notes that if a campaign targets cold contacts or doesn't offer clear value, it's likely to generate more complaints, especially if it's unexpected by the recipient.

Email marketer from Mailjet shares that sudden spam complaint spikes can be triggered by sending irrelevant content, using misleading subject lines, not providing an unsubscribe option, or having a compromised sending IP.

Email marketer from EmailGeeks explains that potential causes are: Google started moving some of your mail into the bulk folder, thus changing the denominator and causing your complaint rate to increase; Someone has compromised your system and is using it to send mail only to Google; (Primarily for ESPs: DKIM replay attack); Someone inside your company did something that was unwise.

Email marketer from SendPulse says that a sudden increase in spam rate can occur if you are sending to inactive email addresses, have changed your sending frequency, or are sending from a new IP address without proper warmup.

Email marketer from Hubspot explains that when recipients mark emails as spam, mailbox providers take note and might start diverting future emails from the same sender to the spam folder, impacting your overall deliverability and sender reputation.

Expert from Email Geeks explains several potential causes for a high user-reported spam rate in Google Postmaster Tools, including Google moving mail to the bulk folder, system compromise, DKIM replay attacks, or unwise actions within the company.

Expert from Word to the Wise explains that increased complaint rates, which drive up spam scores, can be caused by list aging, changes in sending practices, aggressive marketing, or changes to filters.

Expert from Spam Resource highlights reasons for ending up on blocklists, which can suddenly increase spam rates, including spam traps, high complaint rates, and poor list hygiene. Also points out that sudden spikes can be due to compromised credentials or a rogue employee.

Documentation from Microsoft outlines that issues like poor sender reputation, spammy content, lack of authentication (SPF, DKIM, DMARC), and high complaint rates contribute to emails being marked as spam.

Documentation from RFC Editor shares that spam is Unsolicited Bulk Email (UBE) is email that is sent to a large number of recipients who have not asked to receive it. UBE is most often commercial in nature, but can also be non-commercial.

Documentation from SparkPost highlights possible causes like sending to old/unengaged lists, sudden increase in email volume, poor list hygiene, or content triggering spam filters.

Documentation from Google Support explains that a high spam rate indicates recipients are marking your emails as spam. Sudden spikes can result from changes in sending practices, content, or audience.