infrastructure can be perfect and you can still get flagged based on HOW you send.

email providers track patterns. if your sending behaviour looks suspicious, you get throttled. and the worst part about throttling is it's invisible. your emails are still "sending." you just don't know they're being quietly deprioritised.

i know over 20 cold emailers who got wiped out by silent throttling in 2025. most of them didn't realise what was happening until their pipeline had already shrunk.

sending behaviour checklist

• [ ] you're ramping up volume gradually (not going from 0 to 100 emails on day one)
• [ ] each inbox sends no more than 10-15 emails per day
• [ ] your sending is spread across 6+ hours (not all blasted at 9am)
• [ ] you're not sending identical copy from multiple inboxes (triggers pattern detection)
• [ ] your emails have some variation in length and format
• [ ] you're tracking reply rate per inbox (not just aggregate)

throttling detection

you might be getting throttled RIGHT NOW and not know it.

warning signs:

→ open rates dropping gradually over 2-3 weeks

→ reply rates falling even though copy hasn't changed

→ deliverability tools show "delivered" but engagement is declining

→ new inboxes perform well but older ones are dying

if you're seeing these patterns, rotate your inboxes. add fresh domains. check your IPs.