[MlMt] Running MailMate simultaneously in two locations

[Randall Gellens]

On 24 Apr 2023, at 11:32, Glenn Parker wrote:

> I use MailMate on two computers in two physically separate locations. 
> Each instance of MailMate uses a similar set of rules on my primary 
> INBOX to relocate certain incoming email into dedicated folders. For 
> example, the messages from this MailMate forum are directed into a 
> MailMate folder. I realize there are other ways to manage this kind of 
> thing in MailMate (isolating messages from email lists), but use a 
> less sophisticated email client on my Android devices (AquaMail), and 
> this style yields a fairly comfortable workflow for me across all my 
> devices.

Having one client execute rules is a well-known way of using IMAP. In 
the old days when IMAP was first being designed, this was called an 
active client (the client is always on and actively moving/deleting 
messages).

> I have found that I must be careful to avoid running my two MailMate 
> instances at the same time. Otherwise they seem to get into a fight 
> over who is going to execute the INBOX rules. When this happens, it 
> typically generates a bunch of seemingly dire error messages from 
> MailMate, and eventually causes MailMate to take one or more folders 
> off-line.

It won't work to have two active clients, because messages will vanish 
and appear while a client is trying to operate on them. (Unless you 
create some sort of out-of-band mechanism for the clients to coordinate, 
but nothing like that exists now.)

There are some newer IMAP extensions that can help with this, but server 
support is uneven, and I haven't looked into if MailMate supports them, 
and at best they provide some more information about messages and 
mailboxes.

The way to do what you want is to either have one active client that is 
always running, and it is the only client that executes your rules, or, 
use server-side filtering. Some IMAP servers support Sieve, a mail 
filtering syntax. You edit your Sieve rules and the server executes 
them, typically during message delivery, so the rules are executed and 
messages are moved or deleted or replied to or whatever before any of 
your clients sees the message. If your server supports Sieve or another 
server-side filtering solution, that would be safer and more reliable.

> My points here are two-fold. First, if you try the same thing, don’t 
> be too surprised if you run into some complications. So far, this has 
> not resulted in any loss of email for me, but having a folder quietly 
> go off-line while you’re not looking can be confusing.
>
> Second, I’d like to ask if MailMate could be more forgiving when it 
> runs into this particular situation. That is to say, when moving 
> messages between folders using automatic rules, if a message 
> “disappears” during the operation, allow this to be treated as a 
> soft error that can generate an (optional) warning, but don’t take 
> any folders off-line.

The issue is that MailMate doesn't know why a message vanished during a 
move or why the server is reporting an error. It could represent some 
more serious problem.


--Randall