SMTP Email Relay Limit

Mailprotector's SMTP email relay system is intended for human-generated, person-to-person messages with prior recipient consent, recommends limiting outbound sending to 200 SMTP relays per mailbox per hour (counting each recipient in CC and BCC), enforces a maximum message size of 150 MB including all content and encoding overhead, and advises using third-party services for mass mailings.

Mailprotector's outbound systems are designed for human-generated messages for direct person-to-person contact. Any outbound messages should be directed toward recipients with which you have a prior business relationship, have specifically requested contact, or have included their address in your distribution list on a double opt-in basis.

For newsgroup and mass mailings, we recommend a third-party service such as Campaign Monitor, Mail Chimp, or other services designed for high-volume outbound sending. Please read Limitations of outbound relay through Mailprotector for more detail.

Mailprotector email send limit - no hard limit on the volume

Mailprotector recommends keeping outbound sending volume to 200 SMTP relays per mailbox per hour to avoid acceptable use violations. Each address listed in the CC and BCC fields counts against your limit. One relay consists of an email message sent to one address using SMTP. Therefore, you can send up to 200 messages per hour per mailbox.

Mailprotector outbound SMTP size limit

The message size max is 150 MB per message.

NOTE: The size includes text, HTML, images, and attachments. Email encoding can inflate the size of the message. For example, a 100 MB file attachment may grow to 130-150 MB after encoding and exceed the message size limit.

Updated 3 years ago

Blocked File Types and Extensions

Allow List and High Risk Domains