Domain transfer - is email transfer seamless?

I'm moderately experienced with HTML and CSS, but I'm new to hosting and to DH. I don't entirely understand how to transfer my clients' domains into my DH account, specifically their email accounts. There seems to be a possibility of them losing some email during the transfer process, though I find little mention of this. Here's an interesting paragraph from the wiki:

As for the email switchover, as long as you keep your old hosting account for a little while after you make the DNS switch, you shouldn't lose anything. For a while, some emails will go to our servers and some will go to your old hosts...but once the dns propagation is finished, all the email will be going to our servers and you can safely cancel the old account. However, you've still got a problem because you will not be able to retrieve the email which was routed to your old host after DNS starts directing your computer's email client to Dreamhost. Here is the solution: Set up a special email account in a different domain (example: Yahoo, gmail, or your ISP). Just before throwing the switch on DNS, log in to your old web host's control panel and set all of your domain's email accounts to forward to this special account. Then, add the special account to your computer's email client and schedule it to download email. All of your domain's email will immediately be downloaded via this special account, but during DNS propagation it will go more and more back to your domain's account, now hosted by Dreamhost.
http://wiki.dreamhost.com/KB_/_Domains_/_Transfers_/_Transfer_Hosting#How_can_I_seamlessly_transfer_my_site_to_DreamHost_from_another_host.3F
This method is also discussed very briefly in the DH forum post " uninterrupted email while switching hosts?" (October 5, 2007)

Another source suggested that the client should simply check their old account (via web mail) for about a week, then close that account. Seems like an easier method, but then those messages aren't saved as easily.

Is this or some other workaround really necessary for every single email account I ever migrate to DH? I assume this is not unique to DH. Is it routine to some of you, or is this not a big deal and generally ignored? Are my clients apt to lose emails otherwise? When I switch the DNS, is their email client, Outlook or whatever, going to function normally, oblivious to the switch (if it's POP and I set up the same username and password at DH)? Or will it have problems? I want to be careful with my clients' email, but I'm finding little information regarding the possible hazards of the transition period during DNS propagation. I have related questions, but I should perhaps stop here.

Thanks.

I think I understand your concerns, but it seems to me you already have the answers to your question(s) - both the DH wiki methodology and the other information you have found essentially describe the same thing:

You just need to insure that, while the mail is going to one or the other of the accounts (the old or the new account), your client can actually "check" (or "POP") *both* accounts until no mail is received at the "old" account.

As you have seen, there are several ways to do this. I think which way you approach it has a lot to do with your clients' wishes.

As for whether or not such a process is "really necessary", only you and your clients can answer that question. Some provision must be made to keep mail from being bounced (or worse yet, being "received" at a location where your client can no longer access it!) if you want to make sure your client loses no mail. This is a "routine" and "normal" consideration in changing DNS and, while some who do not care about missing some email may ignore it, most consider it a relatively "big deal" and will want some plan in place to minimize the loss of email during the transition.

Whether or not any client settings will need to be changed depends upon a number of factors in addition to just being able to use the same password (such as the login user setup, possible port changes depending upon providers and ISP etc,) so I don't think it is safe to assume that all clients will be "oblivious to the switch" (although some may well be).

--rlparker

OK, thanks. Yes, I want to be very careful with clients' email.

I also wonder if I should tell clients to save an archive of their mail before the switch. Is that sensible or overboard? I have no idea if Outlook, et al. may lose messages due to a configuration error or something.

I think archiving important mail is always a good idea.

Outlook should be already doing that if you are using it as a POP client.

-rlparker