What role do mailbox providers play in email delivery?

Mailbox providers play a crucial role in determining a sender's reputation, which directly influences the deliverability of emails to recipients' inboxes. These providers evaluate various factors to assess the trustworthiness of a sender. This assessment includes analyzing the sender's domain, engagement metrics, bounce rates, and spam complaints.

A positive sender reputation increases the likelihood that emails will land in the inbox rather than being filtered as spam or sent to the promotions tab. Conversely, a poor reputation can significantly hinder email delivery, leading mailbox providers to block or classify emails unfavorably.

The other options don't align with the primary responsibilities of mailbox providers. For instance, they do not send emails or create content but rather assess how emails from different senders will be handled within their systems. While tracking email opens is important for senders, it is typically done by the senders themselves through analytics; it's not within the main functions of mailbox providers.