Right, the welcome form just says "suspension seat post" as your bike — which I'll be honest, tells me you're after info on a suspension dropper/seatpost rather than that being your actual frame. So let me give you the useful version.
The two flavours
There are two things people mean by "suspension seatpost" on an eMTB:
• Parallelogram/telescoping comfort posts — think Cane Creek eeSilk (20mm travel), Redshift ShockStop, or the classic Kinekt. Great on hardtails and gravel-ish trail bikes for taking the buzz out. Not really the tool if you've already got rear suspension.
• Suspension droppers — the interesting one for eMTB. The BikeYoke Divine SL and the Cane Creek eeSilk Dropper exist, but the headline act is the Vecnum NIVO/Moveloc and the newer travel-plus-dropper units. These give you dropper function AND a bit of axial squish.
Do you actually want one on a full-susser?
Honestly, on a full-suspension eMTB most riders here find a comfort post is redundant — your rear shock is already doing that job, and stacking a squishy post on top can make the back end feel vague when you're pushing into corners or pumping terrain. Where they earn their keep is on hardtail eMTBs (Vitus Nucleus E, older Levo HTs) where your backside is the rear suspension.
The trade-offs worth knowing
• Weight — suspension droppers are heavier than a bog-standard Reverb or OneUp, often by 150–300g.
• Insertion depth & stack — the sprung mechanism eats seat tube length, so on a size where you're already near max insertion it can be a faff. Worth measuring before you buy.
• Maintenance — more moving parts, more service. Riders consistently grumble that comfort posts develop a bit of side-to-side play over time.
• Torque — clamp to your frame's spec, usually 5–6Nm on a carbon or alloy collar. Don't wing it.
If you tell me which actual eMTB you're running (frame, and whether it's hardtail or full-suss), your weight, and what's bugging you — trail buzz, big hits, or just comfort on long fire-road climbs — I can point you at a specific post and the right travel. Otherwise I'm guessing at the shape of your problem.
What's the bike and what are you trying to fix?