SMTP or POP3 for Exchange on SBS 2003

Looking for some advice to what is
thoguht to be the best way for getting email? At present we use the pop3 connector to deliver email from ISP (webhost) to exchange on our small business server 2003 (sp1).

What are the advantages of IMAP over POP3. Just that we are getting annoyed at the 15mins pop retreival settings.

paul

 

sorry i mean an alternative to the POP3 connector that is used to deliver mail.

 

How many clients? Might be easier to just let Outlook connect directly to the off site mail server for pop and use exchange for onsite mail.

 

only have 5 clients, just we like the features that exchange offers and happy with things so far. just not sure if IMAP would offer any significant benefits over POP3. The other option would be to get a non-microsoft POP3 connector that would not ahve the minimum 15min time interval.

 

If you just redirect your outlook clients to the pop account you won't loose any of your Exchange features. You can even have Outlook deliver the mail directly to the users exchange mailbox.

 

why not use exchange native mode?

If you do pop you wont have all the good exchange stuff. using exchange with pop is just silly ... i would use OWA before pop.

 

thanks for your advice, basically i have been brought in and told to get an exhcnage serve rup and running so its new to me. i will take the advice of chnaging the mode to Native as it is Mixed and there is no need to support legacy exchange servers as there is none.

The main reason i was using the pop connector is that I didn't want emails bouncing if the server went down, so thats why i did not point forward all smtp traffic directly to my exchange server from my domain host.

 

SMTP and POP3 for incoming mail to an e-mail server

I think there is a little confusion here that I think needs clarifying.

SMTP is the protocol used to communicate between e-mail servers. It is the protocol that Exchange (which is an e-mail server) prefers to use to talk to other e-mail servers. It is a real time protocol, and messages are processed and passed on as soon as they arrive.

E-mail clients (for example, Outlook, Thunderbird, Eudora) can also use SMTP to send e-mails to a mail server. This is why out-going mail at the client is usually set to SMTP.

So SMTP is outgoing only on e-mail clients, but can be both out-going and incoming on e-mail servers.

However, there is an issue with using SMTP for your main e-mail feed if you are not sure you can maintain a permenant connection to the internet. I think this is the problem griffmaster is referring to.

That is, SMTP expects the receiving server to always be available. If one e-mail server tries to send mail to another e-mail server via SMTP and the receiving server is not available the sending server may drop the e-mail message or bounce it (although nowadays a mail server will retry for a day or so before doing this). This used to be a big problem in the days of network dial-up solutions, but is still worth considering even with broadband.

There are three ways of dealing with this problem.
1. Use POP3 to pull mail from an ISP's SMTP server. This fixes the problem because POP3 is a pull system - that is the receiving server decides when to pull the e-mails from the ISP's server and can therefore wait to do it when a suitable connection is available. The disadvantages are:

• E-mail is only collected when a scheduled POP3 connection is made. Therefore there is a built in delay in receiving mail.
• These systems rely on the ISP redirecting all incoming mail into a POP3 mailbox. This can cause e-mail address resolution problems. A problem I see often is difficulting for the local e-mail server to route a message to the correct local mailbox if the recipient was set via BCC:
• You are at the mercy of ISP as regards to POP3 mailbox size. If this is small you may find e-mails get rejected because the mailbox is full.

2. Use ETRN to trigger an SMTP feed. This used to be used a lot on dial-up systems. ETRN allows the receiving e-mail server to send a message to the ISP's mail server telling it "OK - I'm on line, send me your e-mails via SMTP ". The disadvantages are:

• ETRN is a scheduled service like POP3, so you get the same delays.
• Your ISP has to support ETRN. This is less likely nowadays.

3. The ISP installs a system to detect when you are on line and holds the SMTP traffic until it detects you come on line. This is very ISP specific. Most ISP won't do this for you.

So in summary, the choice between an incoming SMTP mail feed to Exchange or using a POP3 incoming feed to Exchange is a balance between:

SMTP - real time delivery and least routing issues.
POP3 - less reliance on internet connection but at the cost of a delivery delay and some routing issues.

 

thanks ReggieB, that has helped clear things up.

The internet connection (ADSL) I have is good but it still has some outages, so i would rather have a method that was less reliant on the internet connection. Your summary [ReggieB] is exactly the problem i face. I am happy with POP3 due to the fact it has "less reliance on internet connection" and i can live with the routing issues. The only annoyance i have with it is delivery delay which is currently 15mins (on the POP Connector). I am not sure whether a product like this http://www.tomdownload.com/internet/tools_utilities/native_pop3_connector.htm
is the only way that i could get round the issue I have with my POP delivery schedule.

I also assume that I should update mode to Native and install Exchange 2003 SP2, i'm just put off as with my luck it will probably stop working lol.

 

POP3 and IMAP to retrieve e-mail from an Exchange server

POP3 and IMAP are two protocols used by e-mail clients (for example, Outlook, Thunderbird and Eudora) to retrieve e-mails from an e-mail server (for example, Exchange). IMAP is the default client retrieval system for Exchange.

The main difference is that:

• POP3 pulls the e-mails from the server and stores them on the local computer.
• IMAP allows the client software to manipulate the e-mails on the server. That is, the e-mails stay on server and IMAP provides you with the tools to manipulate the e-mails on the server.

Disadvantages of POP3

• All the e-mails end up being stored on local PCs. This makes it much more difficult to back-up the e-mails.
• With Outlook, the e-mail get stored in a single PST file. If this file gets corupted, users tend to lose all their e-mails (and contact addresses). Also if the PST file gets to 2Gb, Outlook can stop working. In fact, it is wise not to let a PST file get larger than 1Gb
• You don't get access to the other services IMAP provides such as shared company address books and calendars
• The e-mails are stored on a single PC. If the user uses another PC, they loose access to their e-mails

Disadvantages of IMAP

• As all e-mails are stored on the server, the server needs a very large storage and back up system. Usually system managers need to put in place systems to limit user's mailbox size. Such systems are available within Exchange.
• The system relies on there being a connection to the server. No connection, no IMAP.

In conclusion IMAP gives you the best client access to the services Exchange provides. In particular shared calendars and contacts. Personally, I don't think there is much point having Exchange if you don't pair it with IMAP connection to Outlook for most users. You might as well get a cheaper mail server like MDaemon.

However, there may be some users who need to be able to access their e-mails when they away from the server (field staff, home based users). For these users POP3 may well be the best solution. However, if this is the case for you, I would suggest you look at Exchange's web mail options.

Another consideration is storage and backup. If you don't have the storage on your mail server to store and backup all the company's e-mails then using POP3 may be a solution. However, I would argue that it is not a very good solution and you'd be better advised to increase the storage on the server.

The last consideration is cost. If you are on a very tight budget, POP3 with a cheap e-mail server is an option to consider. If this is the case I would suggest not using Exchange. However, when I say tight, I mean tight. For most companies the extra services that the combination of Exchange and Outlook provides outweighs the expense of Exchange and a server with enough storage space to support it.

 

Griffmaster,

You responded while I was writing my second blathering. I think that will answer your question. I think "Native" mode discussed earlier concerns how e-mail clients (Outlook) connect to Exchange rather than how Exchange connects to other mail servers. Native for Exchange is SMTP with IMAP for client e-mail retrieval.

 

just thought I'd recap to you what I have at the moment in case i am confusing you, as i know that sometimes i have that ability, lol.

I do have an exchange server and all clients use Outlook to connect to it to get mail. All clients have access to the shared folders and calendars. The exchange server gets the mail from my ISP POP box called 'Paul' and it uses the SBS POP Connector to do this. The server then delivers the email to the Exchange Mailbox called 'Paul'. The Outlook client on Paul's PC then connects (IMAP) to the Exchange Server and gets the mail. This is what I think is happening in my situation.

I also assumed that since i am using exchange server for each outlook client to get mail then i do not have the problem with Outlook PST files, as i have none.

As mentioned the underlying method that exchange uses to get email from ISP is POP, but it only gets mail from the ISP every 15mins.

 

Yup! thought that was the problem, but that it was worth clarifying.

The 15 minute limit is built into the POP connector. See "Set a POP3 e-mail delivery schedule" in this MS Article.

If you could reduce the SBS POP connector's scheduled period for download to less than 15 minutes you may get problems with your ISP. That is, they don't like you connecting too often. I'd be very surprised if they let you drop it to less than 5 minutes.

There are third party POP connectors that you could use instead of SBS's POP connection. These may let you get the delay down to 5 minutes. However, their quality can be suspect, and even a good one is adding extra complexity to your set up. I wouldn't recommend using a third party connector unless you have little choice.

Therefore if the delay has to be fixed, changing to an SMTP mail feed is the solution.

 

Thanks reggieB. If i was to go change to an SMTP mail feed, then i would obv need a 100% internet connection, or i would have the problems as prevously discussed. So i presume i am between a rock and a hard place then. I have no problem staying as i am and then reaccessing the email system in a few months to see if SMTP mail feed is the best option.

Thanks for all your help, i guess now i will need to go and upgrade to exchange SP2 and just leave email system for now.

 

It might be worth having a chat with your ISP. If they are set up for business networks access they may have a system to handle SMTP during temporary connection outages. I think you are between a rock and a hard place, but worth a quick phone call before you give up on it.

Good luck with the upgrade.