That's what I call a first-class encounter

The trouble with post boxes is that they really don't have any sense of occasion. I always feel that posting a letter is like launching a ship: an event worthy of public notice. Pearls of wisdom committed to paper, then carefully enveloped and expensively stamped, demand a certain clatm. A smashing of bottles on hulls, I know, may seem a little exaggerated for an electricity bill, and a flourish of trumpets (even of the lone bugle, Last Post variety) not altogether an appropriate send-off for Uncle Ken's birthday card. But the post boxes I encounter don't even say hullo.

The Royal Mail Boxes, particularly on the avenue corners in our neck of the Glasgow woods, are admittedly impressive and venerable. In fact, the word ''box'' fails to do them any justice: they are splendid, columnar, cast-iron strongholds which seem as rooted in the pavement as the ubiquitous lines of lime trees. They are painted a confident, institutional red, and not a few of them have stood where they stand for some eighty years.

For all their antiquity, however, they still receive mail with an undemonstrative lack of interest. Your letter just vanishes into their unfathomable and precipitous depths with little more than a remote fluttering sound, all over in a trice.

I prefer a bit of drama. When I lived in Yorkshire I got to know the time in the late afternoon when the post van careered down the winding country lane from the village post office on its way to the main sorting office. I would flag him down like Dick Turpin. There would be a screeching of brakes as the two vehicles came alongside, sheep would flurry in alarm over the fields, plovers would scream and wheel. The letter would exchange hands, and the money for a stamp.

''Right-ho. I'll bring t' change int' morning!'' and off he'd drive again. That's what I call personal service.

Here in Glasgow it's the post offices which (with a little help from their friends) provide the right kind of atmosphere for letter posting. What they offer is the essential ingredient of slowness. You can sometimes queue for ten, fifteen, twenty minutes. This, I think, is the perfect mark of respect for a letter on the verge of a great adventure, a flight across oceans in a sack, a train journey overnight to London, a van ride to Kilmarnock - even, who knows, a contretemps with an alien customs official. I've never managed to figure out the correlation that exists between delay and elation: but it's certainly a factor in post offices no less (well, perhaps slightly less) than in airports. . . .

So habitual is the post office queue in Scotland that an unwritten code of behaviour has developed. I've come across it nowhere else. Instead of the head of the queue pressing hard up against the person doing business at the counter, it halts at a polite distance, waiting to be called. This means that a large part of the office floor is empty while the tail of the queue is crowded so tightly against the door that new customers have to fight to enter.

Finally you are, yourself, at the head of this queue. All attention focuses on you from the rear. Alertness is vital. Then suddently a voice from behind the bulletproof glass cries sharply: ''Firrst please!''

If you don't move instantly you are liable to be nudged in the back by the wee but urgent Glaswegian next in line. She says, ''That's yeeoo, dearr!'' Thus spurred, you step forward hastily.

''Yes?'' asks the bulletproof girl.

Now, I have discovered that even the busiest post office clerks can be induced to enjoy a little conversation. The thing to do is to catch their interest. Sometimes I try: ''Isn't it great: I've at last managed to reply to my old friend Peter down in Yorkshire to tell him the dwarf conifers he sent arrived safely and are doing fine.''

If you tried that opener on a post box, you wouldn't even get a grunt. In a post office you get, ''Really? Will you be wanting a stamp for yourr letterr then?''

You reply affirmatively. ''Yes, please,'' you say, ''one of your very best.''

Sometimes the smile breaks through at this point; sometimes it doesn't.

''Firrst class?''

''Definitely.''

While the girl hunts around in her stamp book, you have further opportunity to pursue conversational gambits of your own choosing. The beautiful mild weather can be effective. Holidays in the sun have been known to produce vociferous chat. Praise works like a dream - for the admirable efficiency with which she mailed the post card you sent your cousin in Australia a week ago. ''It arrived without a scratch, he tells me.''

If none of these tacks initiates the discussion and sociability you feel are called for, then you may have to recount your Second Class Mail story: the one where you sent a package second class and it took four weeks to arrive. It's strange how a negative narrative almost inevitably leads to a positive response.

''Oh,'' she says, forgetting at last to continue her search for your stamp. ''Oh - I can top that one! We have a regular client who paid a large bill, for about $:500, and posted it second class last Christmas. It arrived thism Christmas!''

''No!'' you exclaim in horror.

''Yes!'' she exclaims in even more horror.

''Well!'' And the odd thing is that we are both smiling and grinning. Why is the incredible so delightful?

Soon the horror spreads to other parts of the post office. The adjacent clerk overhears and pauses in his work, Mr. Burgess's Driving License Application form suspended in midair. ''Did you hear that one!'' he exclaims to Mrs. Burgess.

''No. What was that?''

Mrs. Burgess retells it to her daughter, her daughter to her friend, and eventually it bridges the gap and reaches The Queue. In seconds the entire post office is explosive with jubilant exclamations. It can even spill out into the street: ''Have you heard about. . . ?!''

'You did say you wanted a firrst class stamp, didn't you?'' says the girl, laughing. ''You know, I wouldn't sell one of those second class stamps to my worst enemy!''

Sadly, the time comes when you must leave the party, but you go a happy man. Happy that you have brightened the afternoon for a post office clerk; happy that you've posted your letter by handing it directly to a real live person - instead of dropping it anonymously into a box.