TLS connection per folder to the IMAP server?

#1

I was monitoring the IMAP server logs today and noted that when my eM Client established a connection to the server to sync mail, it did not just establish a single connection. It established a bunch of connections serially. I’m not sure if that was intended or not. Does eM Client establish a separate connection to the IMAP server for every single folder? If so, is it possible to just use a single TLS connection to the server to sync all folders?

#2

Hello,

It is not possible to make only one connection, but it should be only 3 - 4 max at the moment.

One connection is for inbox only.

is this situation like this?

with regards
Jan

#3

I just exited eM Client and the re-connected to my server to watch the logs. I counted 131 times where it appears that TLS connections are made. What I see in the logs are many, many lines like this:

Oct 8 11:03:01 imap[24360]: login: [] PLAIN+TLS User logged in SESSIONID=

Where each of the session ID values is unique.

However, using netstat I can see that there are not so many TCP connections to the server. So, what I am seeing it not TCP connections, but perhaps eM Client is re-issuing the IMAP “login” command over and over?

#4

Hello,

I am sorry for delayed answer, anyway this is simply not possible eM Client is limited to make only 3 in some cases 4 connections at one moment.

with regards
Jan

#5

Right. As I said, I don’t think it’s issuing multiple connections. Rather, I believe it’s issuing the login command repeatedly, once per mailbox. I think it’s the login command that is producing all of the entries in the logs.

#6

Maybe it’s only 3-4 connections at the same time. But I can see in the server log that it makes around 100 in one minute (distinct session ids). So I guess it is one for each subfolder.
That is not what other mail clients do.

Is it possible for eM Client to reuse the connection(s)?

#7

at same time is not same as in one minute, and unfortunately no, this would require eM Client’s connection redesign and that would take way too much time we need to spend on issues and new features.

Jan

#8

It maybe ok on small servers with few mailboxes. On larger installations the admins are not be happy because this is severely flooding the server log. The client could also be a banned by DoS protection.

#9

I don’t think this would result in a ban on the client, because all those server logs appear to be created by just repeatedly issuing the login command, not from multiple TLS connections. This is not horrible, but it is taxing on any installation where the users password is looked up via radius or other network authentication protocol. I don’t have that issue, as credentials are local to our server, but some do use external authentication mechanisms.

#10

I understand that this is not good design for some of our users, but we really can’t afford to remake this when it works for 99.99% of users and for the rest we are usually able to provide some workaround or find fix for that.

Jan