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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

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.

Domain DNS settings:

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):

example.com. IN TXT "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.

Email Client settings

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

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.  Do 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

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.