Port 25 was traditionally the default port used for sending email via SMTP (Simple Mail Transfer Protocol). However, it has been largely restricted or blocked by many Internet Service Providers (ISPs) and email providers due to its association with spamming and malicious email activities. Additionally, Port 25 does not support encryption by default, making it vulnerable to interception.

Port 587, on the other hand, supports STARTTLS encryption, ensuring secure email transmission and reducing the risk of security breaches. This makes Port 587 the recommended and more secure choice for sending emails.