LuxSci

Standard shared hosting: POP, IMAP, and SMTP connection limits

What are the concurrent connection limits for POP/IMAP/SMTP?

In our standard shared hosting environment, we impose limits on the number of concurrent (simultaneous) connections to email services. This is to ensure our servers perform at optimal performance for all customers, to prevent any one client from causing degredation due to making a significant number of concurrent connections. These limits are:

  • POP concurrent connection limit*: 10
  • IMAP concurrent connection limit*: 50
  • SMTP concurrent connection limit: 10

What happens if I reach these limits?

  1. Exceeding the SMTP limit will cause refused SMTP connections
  2. Exceeding the POP limit will cause the oldest POP connections to be auto-terminated
  3. Exceeding the IMAP limit either excessively or for more than a few minutes will cause the oldest IMAP processes to be auto-terminated (i.e. a short spike in connections will not be penalized unless it is a very large spike).

* These limits can be adjusted on a user or account basis if there is a legitimate business need. An additional cost may be involved.

For shared Basic and Premium High Volume accounts, the SMTP concurrent connection limit is 25.

For dedicated Basic and Premium High Volume servers, there is no specific SMTP limit, only what the hardware can handle.