Troubleshooting - Sudden huge spike in spam flagging for GMail

Well, you can check for below:

• Gmail weighs engagement heavily. If recent sends saw lower open/click rates, Gmail may have deprioritized your emails, even without spam complaints.

• Did you send to colder leads, re-engagement lists, or tweak subject lines/templates recently? Albeit, sends are sensitive to small shifts in audience quality or copy.

• Sudden increases in volume or frequency (even legitimate ones) can trip Gmail’s algorithms, especially from a Marketo dedicated IP that's still building or maintaining a reputation.

• Sometimes logic changes in Smart Lists unintentionally widen the net to include unengaged leads, which can drag down sender reputation fast.

Some quick tips below:

• Narrow targeting to high-engagement leads temporarily

• Revert to content (or type of content) that previously drove solid engagement

• Pause sends to cold or inactive leads

• Review Smart List filters and segmentation logic

• Consider warming the IP again if volume dropped and then spiked

Hopefully, this is helpful. Please let us know if you have any further questions.

Know that this isn’t a one-size-fits-all situation. Deliverability issues can come from a mix of factors, like:

• Lower engagement or sending to unengaged lists
• Hitting spam traps
• Changes in Gmail algorithms
• Shifts in content or send patterns

You can start by checking Google Postmaster Tools, running inbox placement tests, and reviewing your DNS and authentication settings. Small changes can have a big impact. Happy to dive deeper if it helps!