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Docker Mailserver
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Best Practices | SPF
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docker-mailserver
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docker-mailserver
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Introduction
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Configuration
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Your Best Friend setup.sh
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User Management
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User Management
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Accounts
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Aliases
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Best Practices
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Best Practices
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DKIM
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DMARC
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SPF
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SPF
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< svg xmlns = "http://www.w3.org/2000/svg" viewBox = "0 0 24 24" > < path d = "M20.71 7.04c.39-.39.39-1.04 0-1.41l-2.34-2.34c-.37-.39-1.02-.39-1.41 0l-1.84 1.83 3.75 3.75M3 17.25V21h3.75L17.81 9.93l-3.75-3.75L3 17.25z" / > < / svg >
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< h1 > SPF< / h1 >
< p > From < a href = "https://en.wikipedia.org/wiki/Sender_Policy_Framework" > Wikipedia< / a > :< / p >
< div class = "admonition quote" >
< p class = "admonition-title" > Quote< / p >
< p > Sender Policy Framework (SPF) is a simple email-validation system designed to detect email spoofing by providing a mechanism to allow receiving mail exchangers to check that incoming mail from a domain comes from a host authorized by that domain's administrators. The list of authorized sending hosts for a domain is published in the Domain Name System (DNS) records for that domain in the form of a specially formatted TXT record. Email spam and phishing often use forged "from" addresses, so publishing and checking SPF records can be considered anti-spam techniques.< / p >
< / div >
< div class = "admonition seealso" >
< p class = "admonition-title" > Seealso< / p >
< p > For a more technical review: < a href = "https://github.com/internetstandards/toolbox-wiki/blob/master/SPF-how-to.md" > https://github.com/internetstandards/toolbox-wiki/blob/master/SPF-how-to.md< / a > < / p >
< / div >
< h2 id = "add-a-spf-record" > < a class = "toclink" href = "#add-a-spf-record" > Add a SPF Record< / a > < / h2 >
< p > To add a SPF record in your DNS, insert the following line in your DNS zone:< / p >
< div class = "highlight" > < pre > < span > < / span > < code > ; MX record must be declared for SPF to work
domain.com. IN MX 1 mail.domain.com.
; SPF record
domain.com. IN TXT " v=spf1 mx ~all"
< / code > < / pre > < / div >
< p > This enables the < em > Softfail< / em > mode for SPF. You could first add this SPF record with a very low TTL.< br / >
< em > SoftFail< / em > is a good setting for getting started and testing, as it lets all email through, with spams tagged as such in the mailbox.< / p >
< p > After verification, you < em > might< / em > want to change your SPF record to < code > v=spf1 mx -all< / code > so as to enforce the < em > HardFail< / em > policy. See < a href = "http://www.open-spf.org/SPF_Record_Syntax" > http://www.open-spf.org/SPF_Record_Syntax< / a > for more details about SPF policies.< / p >
< p > In any case, increment the SPF record's TTL to its final value.< / p >
< h2 id = "backup-mx-secondary-mx" > < a class = "toclink" href = "#backup-mx-secondary-mx" > Backup MX, Secondary MX< / a > < / h2 >
< p > For whitelisting a IP Address from the SPF test, you can create a config file (see < a href = "https://www.linuxcertif.com/man/5/policyd-spf.conf" > < code > policyd-spf.conf< / code > < / a > ) and mount that file into < code > /etc/postfix-policyd-spf-python/policyd-spf.conf< / code > .< / p >
< p > < strong > Example:< / strong > < / p >
< p > Create and edit a < code > policyd-spf.conf< / code > file here < code > /< your docker-mailserver dir> /config/postfix-policyd-spf.conf< / code > :< / p >
< div class = "highlight" > < pre > < span > < / span > < code > < span class = "na" > debugLevel< / span > < span class = "o" > =< / span > < span class = "s" > 1< / span >
< span class = "c1" > #0(only errors)-4(complete data received)< / span >
< span class = "na" > skip_addresses< / span > < span class = "o" > =< / span > < span class = "s" > 127.0.0.0/8,::ffff:127.0.0.0/104,::1< / span >
< span class = "c1" > # Preferably use IP-Addresses for whitelist lookups:< / span >
< span class = "na" > Whitelist< / span > < span class = "o" > =< / span > < span class = "s" > 192.168.0.0/31,192.168.1.0/30< / span >
< span class = "c1" > # Domain_Whitelist = mx1.mybackupmx.com,mx2.mybackupmx.com< / span >
< / code > < / pre > < / div >
< p > Then add this line to < code > docker-compose.yml< / code > :< / p >
< div class = "highlight" > < pre > < span > < / span > < code > < span class = "nt" > volumes< / span > < span class = "p" > :< / span >
< span class = "p p-Indicator" > -< / span > < span class = "l l-Scalar l-Scalar-Plain" > ./config/postfix-policyd-spf.conf:/etc/postfix-policyd-spf-python/policyd-spf.conf< / span >
< / code > < / pre > < / div >
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