# Mail app won't connect or send: errors and fixes

What each error from the OpenEmail mail servers means when your mail app won't connect, keeps asking for a password, or can't send, and how to fix it.

Most problems come from four settings. The user name must be the full email
address. The outgoing server needs its own user name and password. Sending
uses port 465 or 587. The password must still be valid. When something fails,
find the server's reply below.

Check the settings first in
[IMAP and SMTP settings for your mail app](/docs/mail-apps).

## How do I read the error?

Look for the server's reply in the error message, or in the app's details or
log view. Our replies have a code and a sentence:

- **IMAP** replies start with `NO` and a code in brackets, such as
  `[AUTHENTICATIONFAILED]`.
- **POP3** replies start with `-ERR` and a code in brackets, such as `[AUTH]`.
- **SMTP** replies start with a number. A number starting with **5** is
  permanent: sending the same thing fails again. A number starting with **4**
  is temporary: your app can try again later.

## It can't reach the server at all

If there is no server reply, your app never reached us. Check the server
names: `mail.open.email` for incoming, `smtp.open.email` for outgoing. Ports
143 and 110 are closed, so use 993 for IMAP and 995 for POP3. Some networks
block 465 or 587: try the other port, or turn off a VPN and try again.

## It won't sign in, or keeps asking for my password

Find the reply in the first column.

| Server reply | What it means | Fix |
| --- | --- | --- |
| IMAP `[AUTHENTICATIONFAILED] Authentication failed`, POP3 `[AUTH] authentication failed`, SMTP `535 5.7.8 Authentication credentials invalid` | The user name or password is wrong, or the password was revoked | Use the full email address and a current password. If unsure, make a new app password |
| IMAP `[UNAVAILABLE] too many authentication attempts; try again later`, POP3 `[AUTH] too many attempts; try later` or `[LOGIN-DELAY] too many authentication attempts; try again later`, SMTP `454 4.7.0 too many authentication attempts, try again later` | Too many wrong passwords for this address from your IP address | Fix the password on every device, then wait 15 minutes |
| IMAP `[AUTHORIZATIONFAILED] this account has no mail store`, POP3 `[AUTH] this account has no mail store` | The sign-in is right, but this identity has calendars and contacts only | Use it for calendars and contacts, or give it an email address in the [app](https://app.open.email) |
| IMAP `[UNAVAILABLE] backend temporarily unavailable`, POP3 `[SYS/TEMP] service unavailable`, SMTP `454 4.7.0 temporary authentication failure: please try again later` | A problem on our side. Your password was not checked | Wait and try again. Do not change the password |

A reply with "unavailable" or "temporary authentication failure" never means a
wrong password. A "too many attempts" reply usually follows wrong passwords,
often from an old device that still holds the old one.

## It connects, then stops or refuses

These replies come after a successful sign-in.

| Server reply | What it means | Fix |
| --- | --- | --- |
| IMAP `[LIMIT] too many simultaneous connections for this account`, POP3 `[IN-USE] too many simultaneous connections for this account` | Too many apps or devices are connected to this mailbox at once | Remove the mailbox from devices you no longer use, or lower the app's number of connections |
| POP3 `[IN-USE] maildrop already locked by another session` | Another POP3 app is downloading from this mailbox right now | Let one POP3 app finish, or use IMAP on the other devices |
| IMAP `[NOPERM] ... requires a credential with ... access; this one has ...` | The app password was made with limited access, such as read-only | Make an app password with full access for this mail app |
| IMAP `[OVERQUOTA] over quota` | The storage is full. New mail is held back until there is room | Act soon: senders' servers stop retrying after a few days. Raise the mailbox's storage limit in the [app](https://app.open.email), or free space: delete large messages, then in [webmail](/docs/webmail) open Storage details and choose Empty Recently deleted. Deleted mail still counts for 14 days until you do. See [Account limits](/docs/guides/account-limits) |

## It receives mail but can't send

Find the reply your app shows when the message fails.

| Server reply | What it means | Fix |
| --- | --- | --- |
| `530 5.7.0 authentication required` | The outgoing server got no user name and password | Fill in the outgoing server's user name and password. Some apps mark them optional; they are required |
| `530 5.7.0 Must issue a STARTTLS command first` or `538 5.7.11 Encryption required for requested authentication mechanism` | Port 587 was used without encryption | Turn on STARTTLS for port 587, or use port 465 with SSL/TLS |
| `550 5.7.1 sender address rejected: not allowed` or `550 5.7.1 Sender address not permitted for this account` | This sign-in may not send as that address. Sending may also be off for the mailbox, domain or account | Send from an address of this mailbox. If it is yours, check in the app that the domain's sending records are live and sending is not stopped |
| `550 5.7.1 From header address rejected: not allowed` or `550 5.7.1 From address not permitted for this account` | The From line names an address this mailbox does not own | Change the From address in the account settings |
| `550 5.7.1 Recipient <...> not verified for this account` | New accounts send only to verified recipients until review | Add the recipient under Activity › Allowed recipients in the app, or wait for the account review |
| `550 5.7.1 Sending is disabled for this sender` or `550 5.7.1 Sending is disabled for this From address` | Sending was turned off for this mailbox, domain or account | Contact support@open.email |
| `451 4.7.0 sending is temporarily paused for this account, please try again later` | Sending is paused for the account | Check the account in the app, or contact support@open.email |
| `451 4.4.0 Temporary failure, please try again later` | The account reached a sending limit, or a problem on our side | Wait and send again. See [Account limits](/docs/guides/account-limits) |
| `421 4.3.2 rate limit exceeded, please slow down` | Too many recipients in one minute | Wait a minute, then send again |
| `452 4.5.3 Maximum limit of 100 recipients reached` | The message has more recipients than one message may have | Split the recipients across several messages |
| `552 5.3.4 Max message size exceeded` or `552 5.3.4 Maximum message size exceeded` | The message is over 25 MB as sent. Attachments grow by about a third when sent, so about 18 MB of files fit | Send large files as a link |

If your app sends through port 25 instead, the reply is
`550 5.7.1 Relaying denied`. Port 25 has no sign-in. Use 465 or 587.

## It sends but no new mail arrives

Check webmail first. If the mail is missing there too, the problem is not your
mail app: check that your domain's MX record is live, in
[Add your domain](/docs/add-your-domain). If webmail shows the mail but your
app does not, check that the app uses IMAP and refresh the folder list.

## It says it can't verify the server or the connection is not secure

Your app could not confirm it is talking to our server. Do not accept or trust
the certificate when your app offers it. Check the server names:
`mail.open.email` and `smtp.open.email`. Check that your device's date and
time are right. Antivirus software or a company network that scans mail can
also cause this warning.

If you use your own server names, such as `mail.yourcompany.com`, they work
only after their check in the [app](https://app.open.email) passes.

## Still stuck?

Sign in to [webmail](/docs/webmail) at webmail.open.email with the mailbox
password. If that works, the mailbox is fine. Webmail does not test an app
password, so if your mail app uses one, make a new one and enter it in the
app.

Do not remove the account from your mail app to start over until you know
what is stored only on that device. POP3 mail and unsent messages can be lost.
Edit the existing account's settings instead.

When you write to support@open.email, include the full server reply and the
time it happened.

## FAQ

### Why does my mail app keep asking for my password?

The server refuses the password it holds. Common causes are a typo, a revoked
app password, or only the part before the `@` as the user name. Update the
password on every device, then wait 15 minutes if sign-in was blocked.

### It worked yesterday. What changed?

Often the password: an app password was revoked, or a mailbox password was
changed and the old one revoked. If the reply says "unavailable", the problem
is on our side and the password is fine.

### Why does it work on my Mac but not on my iPhone?

Each device stores its own settings and password. Compare the server names,
ports and outgoing sign-in on both. The iPhone may also be on another network
or a VPN.

### Will my message be lost if sending fails with a 4xx reply?

Usually not. A reply starting with 4 is temporary, and most mail apps keep the
message in the outbox and try again. A reply starting with 5 is final: fix the
cause and send again.

## Related

- [IMAP and SMTP settings for your mail app](/docs/mail-apps)
- [Account limits](/docs/guides/account-limits)
- [Add your domain](/docs/add-your-domain)
- [Webmail](/docs/webmail)