IMAPTransfer

It can be used to copy, move and forward emails from one server to another. It can either run just once or it can stay connected to the IMAP server and copy/move/forward the emails immediately when they arrive.

Configuration

The easiest configuration is to use a .yaml file like this:

source:
  server: my1.mailserver.com
  port: 993
  user: user1
  password: password1
  folder: INBOX
target:
  server: my2.mailserver.com
  port: 993
  user: user2
  password: password2
  folder: INBOX
options:
  syncmode: all
  move: false
  watch: false

and then start the program using

java -jar IMAPTransfer.jar -c config.yaml

This example would copy all emails in the folder INBOX from server my1.mailserver.com to server m2.mailserver.com.

Moving emails

If you want to move all emails instead, just set move: true in the file above. Then the emails on the source server will be deleted after they have been copied.

Forwarding emails

The program can stay connected to your IMAP servers and immediately forward all incoming emails from the source server to the target server. It is similar to using a normal email forward (e.g. a .forward file) but fixes a problem:

Let's say a user from mail1.com sends you an email to my1.mailserver.com . So the domain of the sender is mail1.com . Now your server my1.mailserver.com forwards your email to my2.mailserver.com e.g. using a .forward file. That means it will open an SMTP connection to my2.mailserver.com and send mail1.com's email. But there is a problem. If mail1.com has an SPF DNS entry saying "-all", my2.mailserver.com will refuse the email because my2.mailserver.com is not an official mailserver for the domain mail1.com . This will result in an error message being sent back to mail1.com telling him that the email could not be delivered.

One solution is to use Sender Rewriting Scheme (SRS) on the mail server that forwards your emails. However not all hosters support that. Another solution is to use IMAP to forward the email, e.g. using this IMAPTransfer program.

Please be aware that only the spam filter of my1.mailserver.com will be used. When forwarding the email via SMTP also the spam filter of my2.mailserver.com would be used but when using IMAP, the email won't be checked again by the spam filter on my2.mailserver.com.

To use it for forwarding emails you will probably use these settings in your .yaml file:

options:
  syncmode: sincelastsync
  move: false
  watch: true

And if you don't want to keep a copy of the emails on the source server, just set move to true.

syncmode can be all, new or sincelastsync:

all all past and future emails of the folder will be copied/moved
new all existing emails will be ignored and the folder will be watched for new emails, which will then be copied/moved/forwarded
sincelastsync reads the last sync position (i.e. the UID) from the file "imap_uid.txt" (or as configured in the uidfile setting of the source) and start the sync from there. This way it can continue a sync when it was stopped.

watch makes the program stay connected to the IMAP server and watch for new emails. Otherwise, it would exit after it finishes processing the existing emails.

Archiving emails

By setting a local target instead of an IMAP server you can save the emails into local eml files instead:

source:
  server: my1.mailserver.com
  port: 993
  user: user1
  password: password1
  folder: INBOX
target:
  path: myarchive
  folder: INBOX
  compress: true

This will save the emails into separate files e.g. myarchive/INBOX/55.eml where the filename is the UID of the email and the suffix is "eml". Using compress the emails can be gzip-compressed and are saved e.g. into 55.eml.gz.

Restoring emails

To restore the emails from such a directory just write the opposite configuration:

source:
  path: myarchive
  folder: INBOX
target:
  server: my2.mailserver.com
  port: 993
  user: user2
  password: password2
  folder: INBOX

This will write them back from the local files into the IMAP server. Please be aware that it will process all emails in myarchive/INBOX, i.e. the syncmode, watch and move parameters are ignored. It will read .eml and .eml.gz files.

Filter

Maybe you want to copy/move/forward the emails into different folders on the target server. For this purpose there is a "filter" section in the .yaml file:

filter:
  - folder: Mail delivery failed
    subject: ^Mail delivery failed.*

This filter would copy/move/forward all emails with a subject starting with "Mail delivery failed." into a folder named "Mail delivery failed" on the target server. All other emails will be saved into the default folder configured in the "target" section of the .yaml file.

The filter can check the subject, sender and receiver of an email:

filter:
  - folder: Mail delivery failed
    subject: ^Mail delivery failed.*
    sender: .*@example.com.*
    receiver: .*@myserver.com.*

Building

The jar file can be built using

mvn clean compile assembly:single

It can be found in target/IMAPTransfer-0.5-jar-with-dependencies.jar afterward.

dg76/IMAPTransfer