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25mail.st help topics

Mail admin interface

You can log in to get your actual host names.

Domain admin login (email): (the email address you sign up with)
Password: (use the password you entered when signing up on 25mail.st)

In this interface you will be able to manage your email domain.  Create and remove mailboxes, aliases, set up vacation auto-replies, and change other settings.

If you need to reset your PostfixAdmin admin password you can do that on our mail admin password reset page.

End-user interface

Mailbox users can use that login to change passwords, and aliases.

Mailbox users access their webmail interface at: http://example.25mail.st/roundcube

Domain DNS settings:

You can log in to get your actual host names.

You need to set an Email Address (MX) DNS record in order for email sent to your domain to arrive at the 25mail.st email servers.  To do this assign the domain example.com MX record to 'example.25mail.st'.  For example (in Bind):

example.com. IN MX 0 example.25mail.st.

On a web based DNS system (like http://zonomi.com/) you go into your DNS system and set an MX record for example.com with a value of example.25mail.st

You should have no other MX records set.  You do not need to add any CNAME or IP Address (A) records.

You may wish to add an SPF record (which declares which servers can send emails for your domain). Depending on which servers send email for your email address domain something like this may work:

  • Name: example.com
  • Type: TXT
  • Value: v=spf1 a mx -all

You can use add a DKIM (domain keys) DNS record so that 25mail.st will sign emails you send through its servers so that recipients know the email was from an authorized email server.  This will often help those emails be marked as non-spam by the receiver.

  • Name: 25mailst._domainkey.example.com
  • Type: TXT
  • Value: v=DKIM1; k=rsa; p=MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAugM7Sznh/95aE4bcMqjXV+AhZJNBE4BYCFfZKhllAsualaxWhbH74pnlAwCQdY90o2fEGZ5SYJoVKUVoHW58aVj4MSZpDdnWgTn/C+bzG8INK/wMFJY82Lafh2atJJ/Hy7i/1OMYdE6P6Uxlqyx2E7jfsGY5HXkgIdunwj2ihpEMfz+3HQ0QyNSvI6i9BE66XlGz1U3Cys7vaYgxDCni6IGbrYpzgrrlm5xc7Uwtv2sHmiZ7aHqjND+uLUWb7eV4HbP7cUFFZrU0D04szn0zIIcOg/VvuFRuHLgIvEE9xKezJ9ZWpJrCweE+Ps5ftGX0X3jYl71F0uiW9X0PMjXK1wIDAQAB

Note that some name servers, e.g. Bind, may require the value to be split into short (<255 character strings). So for Bind you would add a line like:

25mailst._domainkey.example.com. IN TXT ( "v=DKIM1; k=rsa; p=MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAugM7Sznh/95aE4bcMqjXV+AhZJNBE4BYCFfZKhllAsualaxWhbH74pnlAwCQdY90o2f" "EGZ5SYJoVKUVoHW58aVj4MSZpDdnWgTn/C+bzG8INK/wMFJY82Lafh2atJJ/Hy7i/1OMYdE6P6Uxlqyx2E7jfsGY5HXkgIdunwj2ihpEMfz+3HQ0QyNSvI6i9BE66XlGz1" "U3Cys7vaYgxDCni6IGbrYpzgrrlm5xc7Uwtv2sHmiZ7aHqjND+uLUWb7eV4HbP7cUFFZrU0D04szn0zIIcOg/VvuFRuHLgIvEE9xKezJ9ZWpJrCweE+Ps5ftGX0X3jYl71F0uiW9X" "0PMjXK1wIDAQAB" )

To verify the DKIM entry run:

dig +short -t TXT 25mailst._domainkey.example.com

The mail server will take up to an hour before it begins DKIM signing emails after the DNS record is added.

Use port 587 or 2525 (but not port 25) when submitting emails that require DKIM signatures.

Emails sent with Roundcube webmail will be signed with DKIM too.

Adding a mailbox

You can log in to get your actual host names.

A mailbox is where emails are stored on your 25mail.st server. Each mailbox will have a login. Each mailbox will receive one or more email addresses (you can have multiple email addresses on a single mailbox).

To create a mailbox log in at:`

Domain admin login (email): (the email address you sign up with)
Password: (use the password you entered when signing up on 25mail.st)

From the Virtual List menu select the Add Mailbox option. Then complete the details.

Email Client settings

You can log in to get your actual host names.

For the outgoing server/for sending emails:

SMTP Host: example.25mail.st
SMTP Port: 587, 25 or 2525
STMP Connection Security: STARTTLS

SMTP Authentication method: PLAIN or normal password
SMTP Username: the user’s complete email address
SMTP Password: the one asigned for the user in postfixadmin

For the the incoming server/for receiving emails:

IMAP/POP3 Host: example.25mail.st

IMAP Port: 143
IMAP Connection security: STARTTLS
or IMAPS Port: 993
IMAPS Connection security: SSL/TLS

POP3 Port: 110
POP3 Connection security: STARTTLS POP3S
or POP3S Port: 995
POP3S Connection security: SSL/TLS

IMAP/POP3 Authentication method: PLAIN or normal password
IMAP/POP3 Username: the user’s complete email address
IMAP/POP3 Password: the one asigned for the user in postfixadmin

Thunderbird email client settings

You can log in to get your actual host names.

First you will need to create a mailbox.

From Thunderbird select Tools | Account Settings.

In the account sidebar there is an Account Actions option. Select the Add Mail Account.

Enter a name in Your Name. The email address user@example.com in Email address. And your password in Password. Click continue.

You will likely see a few warning messages. That is expected.

Click Configure manually.

  • Server: use example.25mail.st for both IMAP and SMTP.
  • SSL: Change to SSL/TLS for IMAP, leave as STARTTLS for SMTP.
  • Authentication: use Normal Password.
  • User name: use the full email address (e.g. user@example.com). Do not just use the part of the email address before the @ sign.

If you press Re-test Thunderbird may change some of these options. Change them back to the settings above.

Press Done. You will get a message about Checking Password, OK.

In Account Settings for the new account under Server Settings it should have:

  • Server Type: IMAP Mail Server
  • Server Name: example.25mail.st Port 993
  • User Name: user@example.com

In Account Settings under Outgoing Server for the new account it should have:

  • Server Name: example.25mail.st
  • Port: 587
  • User Name: user@example.com
  • Authentication: Normal password
  • Connection Security: STARTTLS

iPhone email client settings

You can log in to get your actual host names.

First you will need to create a mailbox.

On your iPhone go to Settings - Passwords and Accounts - Add Account. Select the Other option.

Select Add Mail Account.

On the New Account page complete the mailbox user's details.

On the next page, under the IMAP tab complete the details. For Host Name (on Incoming Mail Server and Outgoing Mail Server) use example.25mail.st. The Username value (for both Incoming Mail Server and Outgoing Mail Server) will be the email address (i.e. name@example.com).

You can review the connection options on your iPhone under Settings - Passwords and Accounts. Then select the account you added. Then select the IMAP Account. From there you can review the SMTP (Outgoing Mail Server) settings. The Use SSL option should be enabled. Authentication will be Password. Server port can be 587.

Also on the Account page you can select the Advanced page. For Incoming Settings Use SSL should be enabled, Authentication of Password, IMAP Path Prefix /, Server Port 993.

Outlook email client settings

You can log in to get your actual host names.

First you will need to create a mailbox.

From Outlook select Tools | Accounts.

Select the New Account option from the sidebar list.

Enter an email address associated with the mailbox. Outlook will try to detect the correct email settings. If it prompts you, select the IMAP server option.

On the New Account page complete the mailbox user's details:

  • Account description: use the email address or any description your would like
  • Full name: the mailbox owner's name.
  • Email address: the primary email address associated with the mailbox.
  • Username: this is the full email address. For example: user@example.com. The email address must match the mailbox username (including the @ and the domain part).
  • Password: will match the password you set on the mailbox.
  • Incoming server: example.25mail.st and port 993
  • Enable the Use SSL to connect
  • Outgoing server: example.25mail.st and port 25 (port 587 and port 2525 will also work. Sometimes your ISP will block port 25 and you may need to use these other ports.)
  • Enable Use SSL to connect. One customer reports they needed to use the 'Auto' option.

Mac Mail app email client settings

You can log in to get your actual host names.

First you will need to create a mailbox.

From the Mac Mail app select Mail | Accounts (opens System Preferences Internet Accounts).

Select Add Other Account... option.

Enter a Name (whatever you prefer), Email address (the email address of the mailbox, for example: user@example.com. The email address must match the mailbox username, including the @ and the domain part.), and Password. Press Sign In.

You will get an error, and on the resulting page select IMAP (the default) and your 25mail.st server name (example.25mail.st).

On the next page it asks which services to use (Mail and Notes). Deselect Notes, just leave Mail.

The mail account is now setup.

Edit the description to any name you feels fits.

If you press the Advanced... option for the account. It offers to set a path, no need to do that.

From the Mail client app you can go to Mail | Preferences | Accounts then select the account you added. You can leave Automatically manage connection settings enabled. It will default to Port 587; Use TLS/SSL enabled; Authentication of Password.

If you encounter an issue, Window | Connection Doctor will show progress. If you select Log Connection Activity you can then Show Logs.

Migrate email from another provider

To transfer to 25mail.st: setup you email addresses in our interface.  Add those accounts to your email client.  Verify those accounts work and send email OK.  Change your Email Server (MX) records to point to the 25mail.st servers.  Copy email from your old mail host to your 25mail.st account.  To copy the email just copy and paste (or drag and drop) in your email client between the old and the new account.  Else you could use something like the imapsync tool.

Problems accessing outgoing (SMTP) server with your email client

It is normal that some ISPs block outgoing connections to port 25 for security reasons, this is to avoid normal desktops to send emails and become part of bot net networks when exploited. In case you cannot access port 25, configure the email client to use port 2525 or 587 for the outgoing server.

You can test if you can access the server ports with telnet:

telnet example.25mail.st 25
Connected to example.25mail.st.
Escape character is '^]'.
220 example.25mail.st ESMTP Postfix (Debian/GNU)
221 2.0.0 Bye
Connection closed by foreign host.

Forward one email address to another

In postfixadmin forwards are called Aliases, to add a forward. Click
Virtual List -> Add Alias
You can specify multiple destination email addresses, one per line in the To: field.

An email address that stores a local copy as well as forwards the email to other addresses

It is possible to setup these type of accounts. First you need to create a mailbox in postfixadmin, for doing that:

Click Virtual List -> Add Mailbox

Then you need to configure the alias.

  1. Click Virtual List -> Virtual List
  2. On the right hand side of the recently created mailbox click Alias
  3. Keep the mailbox name in the To: field, this enables the local copy to be stored in the mailbox.
  4. Append any other destinations in the To: field, one per line, as below:

in the example is just the mailbox created in the first steps, you need to keep this alias if you wish a local copy of the email be stored in the mailbox.

Out of office auto-reply emails

In postfixadmin, go to Overview, then select the domain. You should see a list of email addresses in your domain. There is a Set Vacation link for each email address. Click the link for the email address you want. The edit-vacation page allows you to update your auto-reply message. Click "Change/set away message" to activate, or "Remove away message" to deactivate it.

Using user+subaddress@example.com addresses

You can receive email for a user at any user+extension email address. Set up the mailbox as user@example.com (without the extension part).

By default emails sent to this address will be placed in the user's inbox. You can also add server-side filters in the rouncube settings interface to perform other actions (e.g. forwarding to a different email address).

For more information: https://en.wikipedia.org/wiki/Email_address#Subaddressing

Spam Filtering

This webmail application features a nice HTML composing interface. The webmail interface also allows end users to tune their spam filtering settings. For example, in the Roundcube interface go to Settings | Junk. From there you can tweak settings like the mark-as-junk score as well as white- and black-listing email addresses and domains. From the Settings | Filters option you can control whether messages marked as spam are moved to a spam folder or not e.g. based on the X-Spam-Flag setting.

Greylisting can reduce spam, and delay delivery of some emails

The 25mail.st servers have greylisting enabled. When the servers receive an email from an unknown sender, they first reject the email. But then accept it on subsequent delivery requests. This typically stops a lot of spam from 'lazy' spam sources (e.g. exploited 'bot networks). It can also typically cause a 5-10 minute delay the first time when receiving an email from an unfamiliar source.

For more information on greylisting: http://en.wikipedia.org/wiki/Greylisting

Note that this cannot be disabled per domain nor per mailbox.

Note that after the first message we white list the source.  So subsequent messages come through right away.

Note that most large email providers (e.g. gmail and microsoft) are pre-whitelisted.

Email sending rate limits and attachment size limits

25mail.st is not intended as a bulk email sender.  Bulk email sending can have blacklisting implications.  Instead we recommend you use 25mail.st for receiving email and sending normal email correspondence.  And use a specialized service for sending bulk email.  For example, http://sendgrid.com/ or another SMTP server (e.g. the one your ISP provides).

Current limits (subject to tweaking) include: You can send attachments up to 50MB in size.  You can send up to 150MB of attachments an hour.  You can send up to 100 emails per hour.