THE EMAIL PROBLEM

If you buy an item and are having email communication problems (so neither of you is receiving all invoice, shipping or query emails), the problem is in 99% of cases caused by anti-spam or anti-virus filters, either on your PC or at your internet service provider (=ISP).

Don't assume you do not have such filters. These filters are there BY DEFAULT, not by your choice. All major ISP's have these filters in place and many PC's come set up this way.

The remaining 1% non-receipt of emails is usually caused by wrong settings at your Ebay account preferences.

THE SOLUTIONS

1) HOW TO OVERRULE SPAM AND VIRUS FILTERS

Tips to overrule your default email spam filters, listed by email system being used:

EarthLink
Earthlink's default spam filter does Not allow a seller's emails to enter your inbox. Earthlink's Spam setting is set to 'Suspect Email Blocking' is disabled by default, and includes Known spam Blocking. You must activate it yourself and switch it to "Suspect Email Blocking". Earthlink will mark a seller's emails as "Suspect" and Place them in your "Suspect Email" folder.
While viewing one of these messages (a seller's email) in the "suspect email" folder, an EarthLink subscriber can click on a single button that will allow future messages from a seller to pass directly to their inboxes. You should also add any known seller's email addresses to your address book.

Yahoo Mail
Yahoo refers to SPAM as "Spam," and it calls Spam-blocking "SpamGuard." If you are a Yahoo Mail Plus user, then  Spam-blocking is called "SpamGuard Plus." When SpamGuard and SpamGuard Plus are enabled (they are by default), all Spam is automatically sent to the Bulk folder, where it is automatically deleted after thirty days.
To tell SpamGuard Plus not to send a seller's email(s) to the Bulk folder, put a checkmark next to the a seller's email9s) found in the Bulk folder and next click on 'Not Spam'. Regular SpamGuard users can move a seller's email message(s) marked as Spam into the Inbox by putting a checkmark next to the email message and then clicking on Move > Inbox. However, Regular SpamGuard users may still find future seller's email messages in the Bulk folder.

HotMail
HotMail calls Spam "Junk." When the Junk filtering is enabled (it is by default), all Junk email is automatically sent to the Junk E-Mail folder, where it is automatically deleted after five days.
To tell HotMail not to send a seller's emails to the Junk E-Mail folder in the future, put a checkmark next to the a seller's email found in the Junk E-Mail folder and click "Not Junk".
If HotMail continues to consider email messages from a seller to be Junk, click Options, then select Junk E-Mail Protection, next select Safe List. Then type teh seller's email domain name (like "xxxxxxx DOT com") into the page and click on Add.

Microsoft Outlook
Outlook does not have a built-in Spam control, but it can automatically block email messages from appearing from specific email addresses by adding these email addresses to its "Junk Senders" list.
To Unblock the seller's email messages, choose the Rules Wizard from the Tools menu, then click on the Exception List button. Click on Add, and then each time add a seller's known email address(es). Click each time OK to save the changes.

Microsoft Outlook Express 6
Outlook Express 6 does not have a built-in Spam control, but it can automatically block any message from appearing from specific addresses. To Unblock a seller's email messages, choose Tools > Message Rules > Blocked Senders List.
Scroll through the list that appears and highlight any address(es) containing the seller's name. Next click the Remove button, then click OK.

Eudora
Eudora calls Spam "Junk." When 'Junk filtering', called "Spamwatch," is enabled, all Junk email is automatically sent to the Junk folder.
To tell Eudora not to send a seller's email(s) to the Junk folder in the future, highlight the seller's email message(s) found in the Junk folder, and choose 'Not Junk' from the Message folder.
If Eudora continues to consider email messages from a seller to be Junk, add the email address(es) of a seller to your Address Book. Then choose Tools > Options > Junk Mail and place a checkmark next to the Mail isn't junk if the sender is in an Address Book option. Then click on OK.

GMail
GMail refers to Spam as "Spam," and while it doesn't refer to Spam Blocking by any specific name, it is set to block Spam by default. All Spam is automatically sent to the Spam folder, where it is automatically deleted after thirty days.
To tell GMail not to send the seller's Email(s) to the Spam folder in the future, put a checkmark next to the seller's email(s) found in the Spam folder and click on "Not Spam".

Mozilla Thunderbird
Mozilla Thunderbird calls Spam "Junk Mail.", so when Junk Mail filtering is enabled, all Junk Mail is automatically sent to the Junk folder.
To tell Thunderbird to not send a seller's emails to the Junk folder in the future, highlight the seller's email message found in the Junk folder, and click the Not Junk button in the Toolbar. You can also use the keyboard shortcut of Control + J, or you can choose Mark As Not Junk from the Message menu.
If Thunderbird continues to consider messages from the seller to be Junk Mail, add your known seller's email addresse(s) to your Address Book. By default, any address(es) in your Address Book will not be considered Junk Mail.

Apple Mail
Apple's Mail application calls Spam "Junk Mail," and has two modes of Junk Mail blocking. In "Training" mode, the email messages considered Junk Mail are colored brown in the Inbox, but remain visible. In "Automatic" mode, the Junk Mail messages are automatically sent to the Junk folder.
To tell Mail not to send a seller's mail to the Junk folder in the future, highlight the seller's email message(s) found in the Junk folder, and select Message > Mark > As Not Junk Mail.
If Mail continues to consider messages from a seller as Junk Mail, add the seller's email address(es) to your Address Book. By default, addresses in the Address Book are not considered Junk Mail.

Opera M2
When SPAM Blocking is enabled in Opera M2, all SPAM messages are automatically sent to the Spam folder.
To tell Opera M2 not to send a seller's email9s) to the Spam folder in the future, highlight the seller's email message9s) found in the Spam folder, and click the Not spam button in the Toolbar. You can also right-mouse-click the seller's message and choose Mark > Mark as not spam from the pop-up menu.

Yahoo Mail
Yahoo refers to SPAM as "Spam," and it calls Spam-blocking "SpamGuard." If you are a Yahoo Mail Plus user, then  Spam-blocking is called "SpamGuard Plus." When SpamGuard and SpamGuard Plus are enabled (they are by default), all Spam is automatically sent to the Bulk folder, where it is automatically deleted after thirty days.
To tell SpamGuard Plus not to send a seller's email(s) to the Bulk folder, put a checkmark next to the a seller's email(s) found in the Bulk folder and next click on 'Not Spam'. Regular SpamGuard users can move a seller's email message(s) marked as Spam into the Inbox by putting a checkmark next to the email message and then clicking on Move > Inbox. However, Regular SpamGuard users may still find future seller's email messages in the Bulk folder.

2) HOW TO FIX EBAY EMAIL SETTINGS

Check if you have updated your most recent email address in two places on Ebay, at your Ebay account profile as well as in your Ebay notification preferences. It is quite common  that they either of them is stil set for an old email address.

These are the following two preferencess locations on Ebay to change email addresses:

1) In left column (or tabs above) of My Ebay, select

My Account - followed by

Notification Preferences - followed by

Delivery Options, followed by

Show - followed by

Registered email address - followed by

Edit

There you change your registered email address (make sure you Save it).

2) In left column (or tabs above) of My Ebay, select

My Account - followed by

My Ebay Views(in left column) - followed by

Summary - followed by

Email and Contact Information - followed by

Registered Email Address - followed by

Edit

There you change your registered email address (make sure you Save it).