Why Me? Gmail and IMAP Access
A Gmail connection error stating, “Too many simultaneous connections” might be confusing, but it is not uncommon. This issue can be fixed for good so you can access your Gmail in your email program, just as before.
Know the Simultaneous Gmail IMAP Connection Limit
Gmail supports up to 15 simultaneous connections by IMAP.
Dealing with the Gmail IMAP Connection Limit and “Too Many Simultaneous Connections” Error
To fix the “too many simultaneous connections” Gmail IMAP error, try the following tips:
Close any email programs that run in the background on your computers with the Gmail account set up using IMAP; they might keep connections open persistently. Do try to connect to Gmail in your desired email program after each other program you close to identify possible culprits for keeping a large number of Gmail IMAP connections open. Turn off any unused devices (such as tablets or phones): email programs on these devices may be connected to IMAP on the background. Do try your favored application after having shut down each device. If you identify a device as causing the connection failures: Close the email program you do want to use (the one that returned error messages before). Turn the offending device back on. Re-launch your desired email application. Identify and individually turn off email programs (including email programs running in the background). Try connecting in the email program you desire to use after each app to identify the one that causes the connection failures. Identify services that might connect to your Gmail account via IMAP. Disable or disallow services selectively and try checking for messages in the email program that returned errors. You can re-enable and again allow services, of course, after you have gotten your main and preferred email program going. Start with the most important third-party services, and use alternative methods to connect to Gmail (such as OAuth) whenever possible.
Are There Any Other Gmail Limits I Should Know?
To protect its service and users, Gmail has limits on many a thing you can do with email, of course. Most importantly, you can only send and receive messages up to a certain size limit.
For this limit, it does not matter whether you use the web interface or connect through an email client using IMAP (for receiving mail and accessing folders) and SMTP (for sending messages).
Also, Gmail curbs the size of the total data—emails, attachments, etc.—you can keep in your account. You can lift the limit for a fee to store more emails and files.
Finally, you can impose a limit yourself: to make IMAP access faster—for as many connections as are allowed…—, Gmail lets you offer only a certain number of recent emails by IMAP to email programs and services that connect through that protocol.
