Moving email from one server to another

[cheapohubby]

Has anybody tried writing an app that would monitor one server's IMAP folder, and move any emails meeting certain criterion (a week old), to another server?
Does the library support reading an email into ram, rather than to flash? Can it handle two open connections to separate servers?

[mobizt]

No embedded device that has enough memory to keep the message that can be large as hundred kilobytes to megabytes, unless you use PSRAM.

For ESP32, it is possible to open two IMAP sessions because it has enough memory.

Library allows you to access message that is fetching via stream callback.
https://github.com/mobizt/ESP-Mail-Client/blob/master/examples/IMAP/Data_Stream_Callback/Data_Stream_Callback.ino

You can handle the message in that stream e.g. save to filesystem, send to other device via serial port or store in memory which is up to you.

[cheapohubby]

I could use an ESPCam board (2-4MB PSRAM); and a large SDcard as fall back if a message is too large for the ram. So it sounds like it might be feasible. Now it's a matter of deciding if it's worth doing...

[cheapohubby]

Actually, why do I even need to save the entire message? I assume sendStreamCB can be used to write the chunk I just received via the mimeDataStreamCallback? (seems like sendStreamCB is just an internal call used to call the mimeDataStreamCallback; guess there's no easy way to connect an incoming stream to an outgoing one).
Btw; is there documentation I'm missing on the library (beyond the many examples)? Or is it a matter of looking at the source code?

[mobizt]

It's not possible to move or transfer message from one server to another unless different mailboxes on the same server.

The only possible approach is saving the message from one server and append to another IMAP server.

The library does not have the RFC822 message parser or even eml file reader.
Library supports only RFC822 creation then you have to re-construct your RFC822 message from saving message data before using append.

[mobizt]

You should learn the basic of IMAP commands for better understanding how this library or mail app works with mail server.

[mobizt]

You should create an nodejs app to work in this way instead of using embedded device to do this hard work.

[cheapohubby]

Could; but then I'd have to decide where to run it, and maintain that server. An esp32 is self contained, cheap, and low power. Besides, I'm more familiar with embedded firmware than javascript.

[mobizt]

The resource of embedded device is very limited, the data to handle also restricted.

There are many choises to run nodejs or c/c++ IMAP library in Raspbian or linux in single board computers e.g. LattePanda, Raspberry Pi, Onion Omega, and Orage Pi which is better for data rich application.

Embedded MCU or microcontroller is not design for this but for i/o.

It is up to you.