iredmail increase mail attachment size

Default mail attachment size in iredmail is 10 MB. To increase mail attachment size, login to server as user root, run following commands

Here 104857600 is 100 MB in bytes (100 * 1024 * 1024). Change this as required. Sending very large file using mail attachment is not recommended, it is better use file […]

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Zimbra webmail not working on port 80/443

On Zimbra mail server, webmail stopped working on Port 80/443. Admin interface worked properly on url https://hostname:7071/. There is no errors displayed under monitor tab of Zimbra Admin. To fix, run

After running this, netstat -lntp start showing nginx running on port 80 and 443


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Zimbra Mail Server CentOS firewall settings

On CentOS 7 server with firewalld running, used following command to open ports used by Zimbra Mail Server.

See Zimbra, firewall-cmd […]

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Zimbra redirect webmail http to https

After Zimbra mail server installed, webmail work on url https://SERVER-HOSTNAME-HERE/ If you access webmail with out HTTPS, it won’t work. To set HTTP to redirect to HTTPS, login to server as root, switch to user zimbra


Wait few minutes, HTTP link will redirect to HTTPS.

You need to wait few minutes […]

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Install SSL Certificate on Zimbra mail server

Zimbra SSL install

To install SSL certificate for Zimbra Mail Server, login to server, switch to user zimbra

Now create file commercial.key, paste your Private key.

In commercial.crt, paste your SSL certificate.

Create commercial_ca.crt with content of your ca-bundle file.

Verify SSL cerificate

If SSL verified sucessfully, you can install it with command […]

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DMARC is used to protect your email from email spoofing. DMARC use SPF and DKIM record to validate your email. DMARC is a TXT record added in your domain DNS. DMARC record look like

p=POLICY_HERE This specifies what to do with incoming email that fails DMARC. Valid options are none, quarantine and reject. p=none […]

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Postfix disable IPv6

To disable IPv6 on postfix mail server, edit


Replace with

Restart postfix

Method 2


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Configure postfix to relay mails using Gmail

Install postfix

Create file


Save and exit editor. Run

Edit postfix configuration file

Find and remove

At end of the file, add

Restart postfix

Now all mails will be forwarded using gmail. Test Email Delivery Install mailutils

On CentOS

To sent test email, run […]

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Zimbra Unable to validate certificate chain


On installing SSL on Zimbra mail server, i get following error

This was due to SSL cert chain. The ca-bundle file they provided did not work with Zimbra. This is due to some issue with the order in witch CA Certificate files are placed. Here is zimba documentaion related to this issue I […]

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