STO
- Offered from some ESPs and sending platforms, but not all.
- Sending an email at a specific time is based on past subscriber interactions and may not be delivered at the time a subscriber opens their mailbox.
- Requires subscriber-level data tracking.
- Many senders use the same strategy, increasing the chance that your email is delivered at the same time as other senders, negating any benefits.
VTO
- Can be used by any ESP or sending platform.
- Email is delivered when the subscriber opens their mailbox. There is no guessing when to send an email based on past subscriber behavior.
- No personal subscriber data is tracked or shared.
- Subscribers often open their mailbox several times per day, giving Yahoo multiple opportunities to place senders' email in one of the top slots in their message list.
