VayloMailSee pricingWhat the error looks like
A mail provider that refuses a connection usually returns an error to the client, not a clear reason. Gmail's help page quotes the message Too many simultaneous connections, and says it appears when many email clients fetch mail from the same account at the same time.
Symptoms to check for: a sync that stops partway through, a client that repeatedly fails to log in, or a job that works on its own but fails when a second client connects. Gmail suspends an account temporarily, typically for an hour and up to 24 hours, when its server request limits are exceeded. Google recommends that mail clients check for new mail no more than once every 15 minutes.
Limits by provider
| Provider | Concurrent IMAP connection limit | Other IMAP or bandwidth limits | Source |
|---|---|---|---|
| Gmail / Google Workspace | Not published as a connection count. Gmail allows up to 15 email clients to be added at a time per account. | IMAP download 2,500 MB a day; IMAP upload 500 MB a day. When server request limits are exceeded, the account is suspended temporarily, typically for an hour and up to 24 hours. | Gmail help: add Gmail to another client; bandwidth limits; server request limits |
| Outlook.com / Microsoft 365 (Exchange Online) | Not published | No IMAP or bandwidth limit stated on the page checked. | Exchange Online limits |
| Fastmail | Not published. Fastmail limits successful logins, not open connections. | 500 successful logins per user every 10 minutes, across all services including IMAP, POP and SMTP. | Account limits |
| Zoho Mail | 100 concurrent IMAP connections per account. | POP: 5 concurrent connections per account. IMAP fetch: 1 GB per rolling 15 minutes for organisation users, and 250 MB per 15 minutes for personal accounts. | Rates, limits, and policies |
| Migadu | Not published | No IMAP limit stated. Daily incoming and outgoing message allowances and soft storage limits are set by plan. | Pricing |
| Proton Mail (Bridge) | Not published | No IMAP connection, sync or bandwidth limit stated. Bridge requires a paid Proton Mail plan. | IMAP, SMTP and POP3 setup |
| iCloud Mail | Not published | No IMAP limit stated. Sending: 1,000 messages and 1,000 recipients a day, and 500 recipients per message. | Mailbox size and message sending limits |
| VayloMail | No fixed service-level cap; depends on your server and workload | No published benchmark. No fixed VayloMail sending cap; server, recipient and acceptable-use limits apply. | Technical details |
Limits checked 24 October 2026. Providers change limits; check the linked source.
Why providers limit IMAP
Every open connection uses server resources, and every login takes work. A per-account limit stops one client from using up a shared service's capacity at the expense of others.
Fastmail's help article says its login limit exists to guard against poorly built software and misconfigured settings, and that most users are unlikely to reach it. Gmail sets a daily IMAP download allowance of 2,500 MB per account, so a client that downloads a whole mailbox every day can reach it.
How to work within the limits
- Reuse one connection per worker. Log in once, keep the connection open for the job, and close it when the job ends. Opening a new connection for each action uses up connection and login limits. Fastmail counts every successful login toward its 500-per-10-minutes limit.
- Use IDLE where the server supports it. IDLE lets the server push changes over an open connection, so the client does not need to log in again to check for new mail.
- Plan one connection per folder when watching. IDLE watches one selected folder per connection, so watching several folders usually needs one connection for each. Count them before you add folders.
- Sync less. Gmail's help page suggests limiting IMAP sync to folders with 10,000 emails or fewer when clients crash or downloads are slow.
- Close clients you do not use. Gmail's help page suggests closing or signing out of clients you do not need, because each one counts toward the 15-client limit.
- Check less often. Google recommends that mail clients check for new mail no more than once every 15 minutes.
When a dedicated server makes sense
A dedicated server suits a team whose own software reads mailboxes over IMAP, on its own domain, and who want connection capacity to depend on their server and workload rather than on a published per-account number. Connect only to mailboxes you are authorised to access.
VayloMail has no fixed service-level cap on concurrent IMAP. Capacity depends on the server and the workload, and no benchmark is published, so ask support to size your workload before you start. The server costs £35 a month, or £315 billed annually.
It is the wrong choice if you need a fixed number to plan around, or if you need any of the following, which VayloMail does not offer: unlimited storage, guaranteed inbox placement, an uptime SLA, migration, or office-suite features. The technical details page lists what the service does and does not guarantee.
Questions, answered
Why do I get "too many simultaneous connections" errors?
Usually the client has more connections open at once than the provider allows, or it logs in more often than the provider's limits allow. Gmail's help page says the error appears when many email clients fetch mail from the same account at the same time. Reusing one connection per worker and closing clients you do not use are the first fixes to try.
Does VayloMail have a fixed IMAP connection limit?
No fixed service-level cap is published. Capacity depends on your server and your workload, and there is no published benchmark. If your automation opens many connections, ask support to size it before you start.
Which providers publish a connection number?
Zoho publishes 100 concurrent IMAP connections per account. Gmail allows up to 15 email clients to be added at a time per account, which is a client count rather than a connection count. Fastmail publishes 500 successful logins per user every 10 minutes across all services, but not a count of open connections. Microsoft 365, Migadu, Proton Mail and iCloud Mail publish no IMAP connection figure on the pages checked.
Will a dedicated server remove IMAP limits?
There is no published per-account number to reach, because VayloMail publishes no fixed service-level cap on concurrent IMAP. Capacity still depends on your server and workload, and hardware capacity is not unlimited. Support can check whether your workload fits before you start.