POP, IMAP and SMTP Limits

Session limits

Each email account is subject to a maximum limit on the POP and IMAP connections it can open to Qboxmail servers from the same IP address.

The enforced values are more than sufficient for normal use by a user through their email client:

• 50 concurrent sessions for IMAP
• 10 concurrent sessions for POP

This limit may be reached if you configure the same email account on too many workstations and at the same time on several devices such as smartphones, when all these accounts are connected through the same company connection. In this case, the problem appears as a warning about an incorrect username and password. You can reset the number of active connections simply by closing and reopening your email client. If this procedure does not work, there may be other issues to resolve on your PC, for example an antivirus or firewall that does not correctly close sessions even after you have closed the email client, or that blocks TLS connections. Usually, the antivirus vendor’s website provides instructions on how to resolve the issue.

To make sure that the incorrect username/password problem is caused by reaching the maximum number of connections, you can analyze the email account logs using Email log analysis in the Control Panel.

To avoid this type of problem, we recommend configuring your email account on only one PC and, if it is also configured on smartphones and tablets, accessing it through your mobile connection and not through Wi-Fi or ADSL. We also recommend assigning each person a single personal email account (es.mario.rossi@dominio.it) and setting generic email accounts (info@, sales@, …) as Email Aliases to the individual personal email accounts.

For more information about Email Aliases, please read the related documentation.

Thunderbird

If you use Thunderbird, you can change the number of connections opened for each account in its settings: Settings > Server Settings > Advanced > Maximum number of server connections to cache (set it to 1)

More tips on how to configure Thunderbird can be found in this article on our blog:

https://www.qboxmail.it/blog/impostazioni-imap-consigliate-per-thunderbird/

MS Outlook

If you use MS Outlook, you cannot change the number of connections opened to the IMAP server. In this case, we recommend unsubscribing from the IMAP folders you do not use frequently and setting the new message check frequency to between 15 and 25 minutes (this does not affect new message notifications, which remain real-time). The error disappears immediately when you close the email client, because the connections are also closed immediately on the server side.

If the error persists, contact our technical support by opening a Ticket so that we can perform more in-depth analysis.